RECORD Static Frequency -Generators

1 JUL"81 y ELE July 1961 SAC's Primary Alerting System c0 Bell Laboratories Dialing Overseas Calls LIBRARY?)"

Air -Drying for Microwave " %RATOq Systems -y A Self -Protecting Transistor RECORD Static Frequency -Generators

www.americanradiohistory.com F. J. Singer, Chairman W. M. Bacon .T. A. Burton Editorial Board J. W. Fitzwilliam E. T. Mottram R. J. Nossaman W. E. Reichle

H. W. Mattson, Editor A. G. Tressler, Associate Editor J. N. Kessler, Assistant Editor, Murray Hill Editorial Staff M. W. Nabut, Assistant Editor R. F. Dear, Design Editor T. N. Pope, Circulation Manager

THE BELL LABORATORIES RECORD is published monthly by Bell Telephone Labora- tories, Incorporated, 463 West Street, New York 14, N. Y., J. B. FisK, President; K. PRINCE, Secretary; and T. J. MONTIGEL, Treasurer. Sub- scription: $2.00 per year; Foreign, $2.95 per year. Checks should be made payable to Bell Laboratories Record and addressed to the Cir- culation Manager. Printed in U. S. A. © Bell Telephone Laboratories, Incorporated, 1961.

www.americanradiohistory.com Bell Laboratories RE C 4 RD

Volume 39 Number 7 July 1961

Contents

PAGE

235 SAC's Primary Alerting System H. J. Michael and H. M. Prudent

240 Overseas Dialing: A Step Toward Worldwide Telephony O. Myers and C. A. Dahiboni

246 Air -Drying Apparatus for Microwave Systems J. M. Jackson

251 A Self- Protecting Transistor for the E -6 Repeater W. M. Fox

254 Training Simulator for Flight Controllers F. W. Monsees

255 Static Frequency -Generators for Ringing Power W. F. Iiannenberg

258 Sapphires to Protect Telephone Satellites from Space Hazards

John IV. West (leftl and Leif Rongved, surrounded by developmental models of Cover active satellites, discuss a brass frame for holding electronic equipment inside such a satellite (see page 258).

www.americanradiohistory.com Closed circuit teleri,iun cameras focus on briefing oration gathered at these sessions forms basis for officer at sAc's nndcrground command post. Infor- "alerts" issued over Primary Alerting System.

234 Bell Laboratories Record

www.americanradiohistory.com SAC has a force of bombers and missiles capable of prerenting war by deterrence. Bombers on the ground, however, represent a loss of strength in the event of attack. The Laboratories -developed Primary Alerting System gets them "upstairs" fast.

H. J. Michael and H. M. Pruden

SA C's Primary Alerting System

"Peace is our Profession" is the slogan of the To obtain the extra precious seconds needed to Strategic Air Command, whose mighty retaliatory launch a maximum force, SAC now has in opera- force is a major factor in insuring continued tion the Primary Alerting System (PAs). This peace in the world. To fulfill its mission ade- system provides a ready -to -use communication quately, SAC must be ever alert -ready to go into network for broadcasting "alert" announcements action at a moment's notice. to all SAC bases, with emphasis on voice com- Under recently established "airborne alert" munication. It is a permanently assembled net- training procedures, a certain proportion of SAC'S work, furnished as a Bell System service. Spe- bomber fleet is airborne at all times. In addition, cially designed signaling and alarm arrangements a substantial portion of the bombers are on are incorporated to insure the reliability and con- "ground alert" status. These are always ready tinuity necessary in so important a service. to take off, to be airborne within minutes after The Primary Alerting System was developed receiving warning of an attack. In this business, at the request of the Air Force. The A.T. &T. Co., time is precious. Every second cut from the Western Electric Co., and Bell Laboratories time lapse between first awareness of attack to worked with customary teamwork, and the sys- the command to "scramble" means more bombers tem was planned, designed, manufactured, and in the air, ready to carry retaliatory devastation put into service in less than one year. to the enemy, and fewer vulnerable bombers on The Air Force has two prime requirements: the ground. (1) that the network always be immediately avail- Playing a vital role in cutting this time lapse able to broadcast alerts; and (2) that it have is communications -getting immediate word of maximum reliability. To provide the desired imminent attack to all the far -flung SAC bases. availability, the system uses a so- called "hot- line"

July 1961 235

www.americanradiohistory.com arrangement. In this way, the voice path is lines going out to its associated bases. Thus, there always available directly from a controller to all are two separate lines to each Air Force base, bases with no intermediate switching required. laid over separate routes and using separate In order to visualize the function of the alert- equipment; one line goes direct from SAC head- ing system more easily, a brief description of quarters and one goes via the NAF headquarters. SAC'S geographical organization is in order. SAC (For reasons of economy, overseas bases will not headquarters, the nucleus of the command, is in all cases have direct circuits from SAC head- at Offutt Air Force Base, Omaha, Neb. Major quarters, although they will be reached via two subordinate commands within the continental alert circuits.) Each line also appears in a console United States consist of three numbered Air at headquarters, and it is possible to hold conver- Forces and a missile division. These Numbered sation on a selected line without causing interfer- Air Force (NAP) bases exercise authority and ence on any other line. control over all SAC units within three geographical areas covering the eastern, central, and Continuous Supervision western portions of the United States. More than As a further measure to insure reliability, all sixty SAC bomber units are located within these lines, including the circuits on each base, are three areas. under continuous electrical supervision and have As a step in providing the required reliability, suitable alarms at the originating -headquarters the system designers employed dual 4 -wire lines end of each circuit. This provides SAC with an throughout the network. This is illustrated in "up -to- the -second" status check on each circuit. the simplified layout of the network shown below. Because the continuity of all circuits must be All outgoing lines bridge at SAC headquarters checked, even while they are in use, a frequency - and radiate outward to the Numbered Air Force sharing, or "slot," signaling technique is used. headquarters and their associated Air Force This technique requires that a band about 250 bases. At each NAF headquarters, the incoming cycles wide be derived in the normal speech chan- line from SAC is .permanently connected to other nel. All signals are transmitted in this 250 -cycle ` Rf uNf LINES TO All OTHER SAC BASES

SAC HEADQUARTERS LINES TO ALL f OTHER NAF HOS.

AIR FORCE ;4 BASE

LINES TO ASSOCIATED AIR FORCE BASES LINES OVER SEPARATE ROUTES

NUMBERED of communication lines for AIR FORCE Network HEADQUARTERS Primary Alerting System with circuits interconnecting SAC headquarters, Numbered Air Force bases, and their associated air bases.

236 Bell Laboratories Record

www.americanradiohistory.com Senior Controller at SAC underground headquarters in Omaha places a test call over the PAS "Red Phone."

slot. The basic talking and signaling path for all returns an answering pulse at a lower frequency circuits is outlined in the diagram on page 238. to headquarters on the "receive pair" of the As indicated, band- rejection filters isolate all circuit. The originating end of each circuit is telephones and loudspeakers connected to the equipped with a receiving circuit synchronized voice circuits. These filters prevent listeners with the pulse- generator circuit, so that only from hearing the signaling tones and keep voice pulses received at the correct time are accepted currents from interfering with signaling. as valid reply pulses. These receivers are All signals are transmitted over the voice cir- arranged to send alarms to both Air Force and cuits by carrier telegraph terminals, designated Operating Telephone Company personnel if the "43A1," which operate at voice frequencies. Dif- reply pulses fail to arrive after 20 seconds, or if ferent frequencies are used for signaling in too many false pulses are received. opposite directions to prevent confusion in the Circuits on the base itself are also checked for signaling system if the two sides of a 4 -wire continuity by a flow of direct current. If this circuit cross each other. current is interrupted, the tone pulses normally The signals passed through the 43A1 terminals returned toward the headquarters are blocked. are simple and highly redundant. These charac- This causes the circuit to send an alarm. teristics help to insure the reliability of the sys- The alerting and acknowledgment signals, tem, even under adverse conditions. The signals which are sent in opposite directions, are 100 - include those for: testing circuit continuity in millisecond pulses transmitted at the rate of five both directions; sending alerts toward the bases per second for three seconds. The electronic, slow - and acknowledgment signals toward headquar- pulse repeaters at the bases prevent retransmis- ters ; and a call signal toward headquarters for sion of these pulses. non -alert calls. The arrangements for these A call signal of about one second is used for signals and their purposes will be explained below. calling headquarters from the bases. This call sig- Circuit continuity is checked by transmitting nal and the acknowledgment signals are auto- a short tone pulse every three seconds on the matically timed, and are produced by momentarily "send pair" of the four -wire circuit. Each Air operating the proper key. Force base has an electronic pulse repeater that All alerts are initiated and all circuit alarms

July 1961 237

www.americanradiohistory.com and individual acknowledgments are indicated quarters. The base units are suitably packaged console, on specially designed consoles at SAC and NAF and conveniently mounted in a special headquarters. The senior controller's console known as the Combat Wing Console, a Bell Sys- shown on page 237 is equipped with a red tele- tem service furnished at each base. to phone for alerts and a gray telephone for point - The Primary Alerting System is very simple to -point traffic. All other consoles, at both the operate. To initiate an alert from the underground headquarters and the associated bases, have only SAC Command Post at Offutt Air Force Base, the gray telephones. In addition to the common keys senior controller merely picks up the special red and lamps involved in alerting and testing, the telephone and presses the "alert" button on the consoles have individual "appearances" for each alerting console. This transmits both an alerting line. Each line appearance consists of two lamps tone and an alerting signal simultaneously over and an illuminated, non -locking, pushbutton both paths to each base. The former consists of key. The red lamp, which is at the bottom of the alternate spurts of tones at 900 and 1400 cps, line appearance, indicates the status of the par- transmitted as long as the alert button is oper- ticular circuit. If illuminated, it indicates that ated. This alerting tone is received on the loud- the circuit is in trouble. The pushbutton key speakers at all Air Force bases and serves as a above the red lamp is used to select individual warning that an alert announcement is coming. lines for point -to -point traffic, which will be The alerting signal lights the acknowledgment described later. The amber lamp above the push- lamps in the consoles at all headquarters and dis- button is the acknowledgment lamp. Since all connects any point -to -point traffic which may be of these may be illuminated at one time, neon on the lines at the time. After the voice alert mes- lamps are used for both status (red) and acknowl- sage has been broadcast, all base controllers are edgment (amber) lamps to minimize instantane- asked to acknowledge receipt of the message by ous current drain and reduce heat dissipation. pressing the "acknowledge" button. This trans- At the Air Force bases each line terminates mits acknowledgment signals simultaneously to in a loudspeaker that is always ready to receive SAC and NAF headquarters, and these signals ex- alerts, and a telephone set for point -to -point tinguish the individual acknowledgment lamps. traffic. There is also an "acknowledge" button The system is arranged so that a controller at used to return acknowledgment signals when NAF headquarters may also broadcast alerts, in- requested, and a "call" button for ringing head- cluding the tone, signal and acknowledgments,

WARBLE TONE r RED GENERATOR TELEPHONE

BAND BAND RUMINATION ELIMINATION FILTER VOID FILTER SIGNALS

SLOW AND FAST FAST PULSE PULSE AL RECEIVER GENERATOR 43A1 43A1 0 SLOW VF CARRIER VF CARRIER PULSE TELEGRAPH TELEGRAPH REPEATER 'TERMINALS TERMINALS SLOW, FAST FAST AND AND LONG LONG PULSE s- PULSE GENERATOR ACK, LINE RECEIVER VOICE AND BAND AND BAND SIGNALS CALL ELIMINATION ELIMINATION FILTER FILTER

SAC HEADQUARTERS

Schematic diagram of egItipment at SAC headquarters and associated Air Force bases.

238 Bell Laboratories Record

www.americanradiohistory.com vice and to permit rapid and easy detection of troubles should they occur. They duplicated equipment in all critical parts of the system and provided adequate alarms. For example, a voice alert may be broadcast from either one of two completely separate originating red telephone sets, with their associated equipment. They provided duplicate sending circuits, including amplifiers and 43A1 sending units. The output is continuously monitored by feeding back one leg of the output bridge to a monitoring receiver. Should a single pulse of the alerting signals be missed, an alarm sounds, and the alternate sending circuit, which is also continuously monitored, automatically switches in to replace the regular circuit. As previously mentioned, every circuit can be continuously checked, with visual and audible indications of its status. For example, should the circuit fail or its transmission be impaired by as much as 12 db for a period of more than 20 seconds, the red status lamp for that circuit will flash. In addition, at the console a common alarm lamp will flash and a common audible signal will SAC Control Center Air Policemen guard the main sound. When the audible signal is silenced by entrance corridor at Underground Command Post. operation of the alarm release key, the status lamp will light steadily. It remains lighted until the to his associated bases in the same manner. circuit is restored to normal, then goes out. Another feature of Arrangements have been incorporated in the the system is that during circuit times when an alert is not in progress, to permit a fairly complete test of this the indi- important feature vidual lines may be used for point -to -point traffic directly from the console. The controller need between controllers. A headquarters controller, merely hold the continuity check key operated using the gray telephone handset associated with for a period of 20 seconds. This key blocks the console, may select any desired line merely the check pulses from going out on the line, for as long as it is by pressing a nonlocking pushbutton on his operated. When no return pulses console and calling in the selected remote point are received, the alarm circuit starts "timing." At by voice. Conversely, a base controller may call the end of the 20- second interval, all status lamps headquarters by operating a pushbutton that will flash. This not only checks the lamps, but transmits a call signal toward headquarters. On the alarm circuits as well. receipt of this call signal at headquarters, the System to Be Extended associated line lamp flashes at all console positions, which are in multiple, and an audible All reports from the Air Force, as well as those signal sounds. When the call is answered at one from the Operating Telephone Companies who of the console positions by operating the "line" provide and maintain this system, indicate that key, the lamp will flutter at this position, indi- the Primary Alerting System has been performing cating that this is the connected line. At all other satisfactorily in all respects. The system is now positions, the lamp for this line will be steady. being extended to all of SAC'S overseas bases. This connection may be released either by The Primary Alerting System is an excellent selecting another line or by momentarily operat- example of how the Bell System team, in this ing the common "release" key. If this type of case spearheaded by the Systems Engineering call is in progress at a time when an alert is to experience of the Laboratories, is contributing be transmitted, operation of the alert key will im- every day to the defense of our country. This mediately disconnect it. contribution to the deterrent might of the The designers of the Primary Alerting System Strategic Air Command will hopefully lead to have made special efforts to assure continuous ser- an even more important goal -world peace.

1961 239

www.americanradiohistory.com special operating requirements There will be a new supervisory signaling cities. Similarly, plan that will be the same in both directions are limited to staffs in these cities. in respect to format and frequencies. The European plan, on the other hand, prefers Address information will be sent by multi - two types of operation called "terminal" and frequency pulsing at 10 digits per second. "transit," depending on whether the call is routed All cable circuits will handle two -way traffic directly to the terminating country or switched (traffic originating at either end). through another country. If the call is terminal, Only machine access will be allowed to trans- the complete national number is sent ahead. If atlantic channels. the call is transit, only the country code is sent In the proposed transatlantic network, the num- to the transit points. The terminal country, when bering plan used in Europe will meet CCITT it is reached, requests the language digit and na- recommendations ; North America will use the tional number. Although this type of operation standard North American plan. Each country has the gateway -city advantages of limiting the will maintain the internal features it likes. For requisite special equipment and operating pro- European international calls, the CCITT number- cedures, it has the present disadvantage that all ing plan uses a two -digit country code, a language calls using the same country code must be routed digit, an area code which may be a single digit, via a single city. Thus, even though a short, di- an office code and a line number. On a call to rect route may exist between two cities, a call London from any other country in Europe, for between them may have to be directed over a example, the dialing might proceed as shown in longer route through that single city. The alter- the table below. native to this plan is the use of extra codes or more complicated translation. DIGITS DIALED SWITCHING INFORMATION Ultimately, transit operation may be needed for international alternate routing. In prepara- American gateway city 44 Country code, United Kingdom'; tion for this, the North equipment will be designed to send both terminal 2 Language digit and transit signals. On calls from Europe to North America, no distinction need be made, be-

1 Area code, Londo cause on this continent the same mode of operation serves all calls. In every case the complete address 222 Office code information is sent and received and the same group of registers is used for "via" and "termi- 1234 Line number nal" traffic. The CCITT recommends two kinds of registers at each switch point, a two -digit regis- The language digit, the second entry in the ter for transit calls and (usually) a ten -digit table, denotes the language of the calling country. register for terminal calls. The language digit This is to ensure that calls requiring operator is stored in the trunk circuit, not in the register. assistance in the called country will be directed The language digit represents a small problem, to an operator who speaks the language of the though a practical rather than a technical one. calling country. The office code will not neces- On calls from North America to Europe the lan- sarily contain three digits. guage digit must be sent and it will be inserted The arrangements will not be quite the same in by switching equipment. On calls in the other di- both directions on the transatlantic circuits. rection, however, it is not practical to have assist- Mainly because of differences in numbering and ance operators in the United States who speak switching philosophy, some aspects of dialing the languages of Europe. Therefore, by agree- from North America to Europe will vary from ment, all calls to the United States will be handled dialing in the other direction. The major differ- by European operators who speak English. ence is the "gateway city" concept of the United There are other numbering problems besides States and Canada. With this mode of operation, those discussed. One becomes immediately appar- calls to Europe from any point of origin in either ent with a glance at the dials used around the country will be routed through a gateway city - world (see photograph on page 243). On the New York and Montreal are typical -and dialed Swedish dial, for example, the numeral "0" is in from these points. This is a very manageable the position of the numeral "1" on the other dials. concept because special equipment for overseas Mechanical translation may be necessary to recon- dialing need be installed only in the gateway cile this dial with others. The differences between

442 Bell Laboratories Record

www.americanradiohistory.com SWEDEN HOLLAND, GERMANY DENMARK AND ITALY

ENGLAND FRANCE UNITED STATES

Telephone dials from several countries showing some of the variations in lettering and numbering. the English dial and the American dial are slight example. Timing or special translation is used to and operators could be trained to make the nec- indicate that the last digit has been received. In essary translations between England and North London, the area code, "1," indicates that nine America. But for customer dialing, the problem digits (prefix "0" followed by eight digits) will may be somewhat greater. When customer dial- be dialed. In other areas the number is consider- ing is eventually introduced, all- number calling ed complete if, after a fixed time, no further digit will probably be adopted. is received. When operators dial, an end- of -key- ing signal will be transmitted to indicate Difference In Numbering Plans that the number is complete. Another problem arising from the difference in Another problem is that differences must be numbering plans has the same general outline- reconciled in modes of assistance operator and a minor difficulty if operators dial, but more seri- address signaling. The CCITT proposes either an ous if customers dial. This problem stems from arythmie or a binary code. Each code has 16 pos- the idea of a "closed" or an `open" numbering sible signal combinations; ten represent decimal plan and the methods of determining that full digits, the eleventh and twelfth signal "Code 11" address information has been received. and "Code 12" operators for assistance. These last In the North American (closed) numbering combinations correspond, respectively, to the plan, senders and registers "count" the digits that North American 3 -digit inward operator code are dialed and "know" when the last one has been "121" and the 4 -digit delayed call operator code received. This arrangement can be made because "115X." Three of the remaining four combina- there are a fixed number of digits for each tele- tions in the CCITT code are spares, the other in- phone number. In some European (open) plans dicates end of pulsing. the number of digits varies. Eight to ten digits not For supervisory signaling the problem is a bit including the prefix "0" are used in England, for more complex. The CCITT recommends "spurt -type"

July 1961 243

www.americanradiohistory.com signaling in which there are tones on the line only ous line sequences- connect, disconnect, on -hook, when trunk control, status, or address informa- off -hook -are represented in the CCITT plan by tion is transmitted. When the line is idle or dur- spurt signals of fixed duration and a specified coming conversation no tones are present. The North bination of frequencies. To assure a high degree American network, on the other hand, uses con- of accuracy, acknowledgment signals are needed. tinuous supervisory signaling in which there is a They are not needed with continuous signaling. low -level tone always present on the line when it The supervision problem is further complicated is idle. Interruptions of this tone transmit the by TASI. Continuous tone cannot be used on this signaling sequences. When signaling is completed system because its central idea is that the absence and conversation has started, the tone is removed. of any tones or speech energy on a channel indi- Another point of comparison is that the vari- cates that it can be switched instantly to another

COMPARISON OF TRUNK CONTROL AND STATUS SIGNALS BeIISÿ Signaling for Transoceanic TASI SF Signaling for Intertoll Trunks Derived Trunks (2 -way Operation) (2 -way Operation) 2600 Frequencies CPS om Frequency = 2600 CPS 2400 CPS

Direction of Transmission Direction of Transmission:

Idle Condition

Seizure No Tone

Delay Dial No To No Tone

Proceed To Send No Tone (Start Dial)

Address Signals MFKP MFKP

Customer Answer No Tone o Tone No To

Coiled Customer Hang -Up No Tone No Tone (On Hook, Clear Back)

Disconnect- Forward (Clear- Forward)

Disconnect- Acknowledge (Release Guard)

Ring Forward No Tone No Tone (Forward Transfer) 70 -130

Tone Tone Busy - Reorder -No Circuit Audible Audible No Tone (Busy Flash) (30, 60, 120 IPM) (30, 60, 120 IPM)

It Continuous Tone For Calls to United Kingdom & in Milliseconds Europe, a Busy Flash Signal I I Duration of Pulses Indicated 850 or an Audible Tone Trunk control and status signals as they are used on present Bell System and on transoceanic trunks.

244 Bell Laboratories Record

www.americanradiohistory.com Over-all view of the Long Lines overseas switchboard room at the A.T. &T. Co. in New York City, one of the gateway cities.

talker. The signaling plan proposed for the trans- volumes of traffic than had existed previously. atlantic facilities is, therefore, a compromise be- Traffic doubled in the year following the cut -over tween spurt and continuous signaling ; each type of the first transatlantic cable to England. Con- is used where it is most advantageous. The chart versation time per call also increased. An increase on the opposite page compares the types of sig- in traffic has occurred with each new cable and it nals used for TASI derived trunks with those of can be predicted for planned cables. So the future standard North American plan. of telephony is one of continued growth ; its form It is important to remember that the trans- is anybody's guess. atlantic network will be compatible with both the There are clear indications, however, that European and the North American network, and temper the guess with fact. It is quite likely that that all countries will retain their internal fea- in the future, satellites will be used for intercon- tures. Thus, in the matter of signaling, a converter tinental calls. Cables will, of course, be used for will be used at each terminal to accept the type diversity and for protection against interference. of signaling used on TASI and convert it to the In fact, some cable operating and signaling meth- type of signaling used either in North America ods may be adapted to satellite operation. World- or Europe. (See diagram on page 241.) wide calling with satellites will require a complete On the matter of trunks, CCITT operation in reappraisal of existing numbering, trunking, sig- Europe is generally limited to one -way trunks. On naling, transmission and switching plans. Indeed, the transatlantic circuits, trunks will be des_gned so great is the promise of satellites that work has to handle calls originating at either end. The already been started on worldwide numbering. economies of two -way trunking are important, Transmission, signaling, and trunking will be and for Europe, this type of operation will eventu- studied too. Intercontinental centers will probably ally become standard where it is economical. perform the functions on a worldwide basis that Economy -at least in the narrow sense of the regional centers now perform on a national basis. word -is, of course, not the only object of the deci- The horizons of technology broaden with new pos- sion to use two -way trunks. Nor, indeed, is it the sibilities, and the physical horizons seem to grow aim of any other change or development described closer as this technology brings nations to only in this article. That aim is faster, more efficient seconds apart. handling of international traffic. Paradoxically, We are often told that the only real barrier be- one result of improved methods of transmission is tween nations is their inability to understand one that they usually perpetuate and even increase an another. Understanding waits on a transfer of aspect of the traffic problem that they were in- intelligence one to the other and the basis of this tended to solve -its volume. is a transfer of information. In a very real sense, It is almost a truism that message circuits add- the ultimate refinement in communications is not ed to a crowded route will stimulate even greater merely of the future, but will help to shape it.

July 1961 245

www.americanradiohistory.com When moisture accumulates in waveguides and antennas it may damage microwave signals. Therefore, Laboratories engineers bare designed special apparatus to supply dry air under pressure to those vulnerable components of microwave systems.

J. M. Jackson Air- Drying Apparatus For Microwave Systems

small Daily, over five million cubic feet of dry air are early systems, which required a relatively which supplied to the waveguides and antennas of the volume of dry air, to those presently used, dy- Bell System microwave network. Delivered by de- require a substantially greater volume-was hydrators designed at Bell Laboratories, this vol- namic adsorption. Simply, this means that ambi- bed; the ume of dry air is a continuous guard against the ent air is passed through a desiccant is deliv- accumulation of moisture within these critical desiccant adsorbs moisture and dried air bed in the components of microwave systems. ered to the system. When the desiccant is reactivated; Moisture in the antenna and waveguide net- large apparatus nears saturation it works of microwave systems is a serious deterrent in the smaller apparatus it is replaced. TD -2 microwave to good transmission characteristics. A layer of The first transcontinental in the 3700 - condensed water within the waveguides or on re- route, established in 1951, operated band. Ini- flective surfaces of certain types of antennas may to 4200 -mc common carrier frequency -lens antenna result in intolerable signal attenuation and some- tially, this system used the delay only times may completely interrupt transmission. To (RECORD, February, 1952). In this system, prevent or minimize the effects of moisture, the the waveguides were pressurized. To prevent waveguide networks are filled with dry air under dried air from entering the antenna, the wave - ; one low pressure. guide run is equipped with two "windows" The story of improving design of air- drying placed near the repeater equipment, another near apparatus follows closely the story of new devel- the antenna. The windows are electrically trans- opments in microwave systems. In general, the parent, but act as gas dams to confine the dry air problems involved in the design of air-drying to the section of the waveguide run between them. apparatus were problems of volume and pressure. With the volume to be maintained under dry - The basic design principle adopted by the Labora- air pressure thus limited to that of the waveguide tories for all dehydrators -from those used with between the antenna and the repeater bay, only a

Record 246 Bell Laboratories

www.americanradiohistory.com few cubic feet of dry air are needed each day. For these low flow rates very large air -drying apparatus would be impractical. Therefore, Laboratories engineers designed small wall- mounted dehydrators to furnish several weeks of drying service with one desiccant bed. A visual indicator on these units warns local maintenance personnel when the relative humidity of the delivered air exceeds a critical value. The desiccant bed is then reactivated or replaced. In recent years, the rapid growth in long - distance telephone and television transmission pointed up a need for a microwave system capable of operating simultaneously in several common - carrier frequency bands. To fill this need, the Laboratories developed the horn -reflector antenna and its associated circular waveguide (RECORD, November, 19551. Air Pressure Problems of Horn Reflector The incorporation of the horn -reflector antenna in both new and existing microwave routes, nec- ., Tiff.;. essarily posed new problems of air pressure maintenance. These problems can be presented more clearly if we first consider the structure of the horn -reflector antenna. This antenna is approximately 22 -feet long, 11- feet wide and 10 -feet deep; its internal volume is slightly over 300 cubic feet. A thin plastic cover -also called a "window " -covers the face of the antenna. This cover, which has an area of approximately 70 square feet, protects the inside of the antenna from adverse weather conditions. The antenna is assembled from several sections bolted together at flanged, gasketed joints. The Antenna tower at Backhorn Mountain, (,luwado, bolted construction and the temperature and microwave relay station. The 50-foot tower stands weather conditions to which the antenna is ex- on a ground elevation of 8,306 feet. Mounted on it posed make it almost impossible - to ensure a corn are both delay -lens and horn-reflector antennas. pletely airtight assembly of the sections. This leads, as we will shortly explain, to air -drying ice could continue with little i'1 effect. Actually, problems of a somewhat different nature. a two -fold benefit is derived from the pressure of With this new antenna, Laboratories engineers dry air. Not only does it combat the entrance of decided to pressurize the horn as well as its asso- moisture into the antenna, but its action in keep- ciated circular waveguide to prevent moisture ing the window bowed out assures a constant dis- condensation within the antenna. One important tance between the window and the reflecting factor in this decision was a problem arising surfaces of the antenna. This distance is critical from the plastic window. because the continual change which occurs if the It is obvious that with the horns mounted on window is allowed to flutter can degrade trans- towers rising to heights of 400 feet, the thin win- mission quality. dow would "flutter" during windy periods. This With the horn antenna, dry -air pressure must action is detrimental to transmission. A low pres- be maintained at only a few tenths of a pound per sure of dry air within the antenna offsets the square inch. Greater pressure may rupture the wind load, the window tends to "bow- out," and window, and the antenna and waveguide network flutter is reduced. could then fill with rainwater and service would In this connection, it is interesting to note that be disrupted. should the window rupture in dry weather, serv- Another reason for pressurizing the horn is the

July 1961 247

www.americanradiohistory.com extreme difficulty, previously pointed out, of oped new dehydrating apparatus which can fur- achieving an air -tight assembly of antenna sec- nish up to 400 cubic feet of dry air per hour at a tions. By careful design of gaskets and judicious delivery pressure of only a few tenths of a pound choice of gasket material, air leakage can be held per square inch. to a few cubic feet per hour (RECORD, April, The new equipment comprises a centrifugal air 1956). But even this relatively small leakage is blower, two desiccant -filled drying towers, and a many hundred times that normally experienced in humidity -operated cycling mechanism. In a con- earlier systems where only the fairly air-tight tinuous cycle, one tower supplies dry air to the waveguide networks are pressurized. Thus the waveguides and antennas while the other is re- unique air -drying problem presented by micro- activated. The operating scheme of this dehy- wave systems using the horn -reflector antenna drator is shown in the diagram on this page. In was one of furnishing a constant large volume of the diagram the light color represents dry air dry air under very low pressure. which is delivered to the antennas and wave - To solve this problem the Laboratories devel- guides, the dark color represents ambient air cycled through the tower being reactivated. The blower delivers ambient air to one of the drying towers where the moisture vapor is adsorbed by the desiccant bed. Dry air is then piped AIR INLET BLOWER THROUGH FILTER 1 to the waveguides and antennas. The quality of the air delivered to the waveguides is continuous- PURGE EMBEDDED HEATER VALVE ly monitored by a humidity sensing element. (THERMISTATICALLY When the relative humidity of delivered air CONTROLLED) 4 -WAY reaches a predetermined low value, the system is VALVE automatically cycled ; the spent bed is purged with ambient air and the air to be dried for the waveguides is routed through the second tower. Thermostatically controlled heaters which are embedded in the drying agent then reactivate the spent bed. Cycling the towers on a humidity basis- rather than on the basis of a preset elapsed time, which GEARHEAD MOTOR was employed in earlier models of dehydrating equipment -results in efficient use of the full drying capacity of the desiccant and has the added

PURGE advantage of a decrease in power consumption. A AIR may be used for drying for a minimum of EXHAUST tower severe conditions of flow DESICCANT 12 hours under the most rate, temperature and humidity. It may be used for periods of several days under more temperate

DRYING TOWER DRYING TOWER conditions ; for example where ambient operat- NO. 1 NO. 2 ing conditions are milder and the leakage rate HUMIDITY the antenna system is lower. SENSING from TO ELEMENT LOW I PRESSURE GEAR - TO Reactivation Cycle HEAD PURGE TO ALARM DRY AIR TO MOTOR VALVE HEATERS WAVEGUIDES The cycle of reactivation comprises periods of AND heating, purging and cooling. The heated desic- ANTENNAS CYCLING MECHANISM cant releases moisture, which is purged from the CONTROL HUMIDITY CONTROL AND ALARM tower by a small flow of ambient air. When all moisture is purged from the tower, the thermo- MOIST AMBIENT AIR stat turns off the heaters and the solenoid control ESSENTIALLY DRY AIR valve stops the flow of ambient air. The reacti- Diagram showing the flow of air th> Hoyh the dry- vated tower is cooled by radiation until the appa- ing tower of dehydrator to waveguides and an- ratus recycles. tennas. The apparatus constantly uses one tower Two sizes of dehydrators have been developed to supply dry air while the other is reactivated. at the Laboratories. The larger apparatus, used

248 Bell Laboratories Record

www.americanradiohistory.com F. R. Kappel Stresses Defense Communications

The communications industry must do every- thing possible to satisfy military requirements for defense communications, Frederick R. Kap- pel, President of A.T. &T., said recently. Speaking before the annual convention of the Armed Forces Communications and Electronics Association in Washington, Mr. Kappel said industry must use initiative and creativeness to search for answers on its own "to help build our national strength." In defining the Bell System's responsibilities for defense communications, Mr. Kappel mentioned several evidences of "our deep concern." He noted, "Work started more than seven years ago to build extensive long distance communications routes to avoid critical target areas." Author J. M. Jackson inspects control mechanism Also, construction started last year on a new of air -drying apparatus. A simple schematic of hardened cross -continent coaxial cable, entirely the mechanism is shown in the preceding diagram. buried from end to end. On this cable, repeater and switching stations will be installed in heavily primarily at main and terminal radio -relay sta- reinforced underground vaults, and certain key tions with as many as twelve horn -reflector sys- stations will be manned around the clock. tems, furnishes up to 400 cubic feet per hour. A Mobility as a protection for defense communi- smaller unit, which is similar in design, is used cations is receiving serious attention. One of its at intermediate stations with a maximum of four many aspects, Mr. Kappel said, is the possibility antenna systems and has an output of 100 cubic of an airborne microwave system linking key feet per hour. areas by radio relay stations on circling aircraft. Several hundred dehydrators of this general de- Studies show this idea deserves "full considera- sign are in service throughout the Bell System tion," he added. microwave network. They are designed to operate As to satellite communications, Mr. Kappel said in the most severe temperature and humidity con- "We have stated many times that both technically ditions experienced in the continental United and financially we are ready to move on the double States. Dehydrators of this type have been modi- as soon as launching and other arrangements can fied slightly to meet other specific temperature be made with the Government. and humidity ranges. For example, with appropri- Every feasible technical step to insure sur- ate modifications they are used with the White vivability (in military communications) must be Alice communications network in the far north employed, Mr. Kappel said. But at the same time, (RECORD, August, 1958). he added, let us remember human experience and The story does not end here. The excellent serv- competence. ice records obtained over the last several years "Thousands of telephone people all over this with the air -drying apparatus described in this country are trained and conditioned to deal with article have not merely reaffirmed the efficacy of the unexpected," he said. "They have a vast pressure maintenance in suppressing the effects amount of knowledge and down -to -earth operat- of moisture. Rather, they have been a stimulus to ing skill, along with a natural instinct to fix engineering research on new techniques and new whatever may go wrong." methods of drying air. Continuing studies at the "All of us, associates and competitors alike, Laboratories have resulted in a simpler, more are united in devotion to the great task of build- compact, and less expensive air dryer (RECORD, ing the nation's defenses as strong as they ever January, 1960) designed around other principles need be," Mr. Kappel concluded. Serving the of moisture removal- compression, refrigeration Armed Forces as efficiently as possible is a clear and expansion. obligation and "we intend to meet it."

July 1961 249

www.americanradiohistory.com www.americanradiohistory.com A new transistor has been developed at the Laboratories that resists large residua! surges of lightning and does not need the secondary protection of diodes. This device makes a big contribution to the success of another new development, the E -6 repeater.

W. M. Fox

A Self- Protecting Transistor For the E -6 Repeater

Thousands of times every year foreign poten- telephone systems. However, it was fairly costly. tials emanating from lightning attack the vast The importance of the economic factor was outside plant of the Bell System. Central office pointed up when Laboratories' engineers esti- and station equipment would suffer severe dam- mated that substantial savings to the Bell Sys- age if the full voltage of these potentials was tem, and thus to its customers, would result if impressed on telephone circuits. In fact, light- vacuum tubes could be replaced by transistors in ning damage to this equipment is negligible; repeater circuits. Repeaters are electronic devices protectors installed near customer's lines and at which compensate for signal losses on transmis- terminal equipment locations have proved highly sion lines between offices. They are used so widely effective in warding off excessive voltages. In the in the modern telephone plant that estimates past, carbon -block protectors have been used, but showed a potential savings of two to three -and- as transistors and semiconductors find greater one -half million dollars in a year's production. The application in communication circuits, new pro- longer life and lower power consumption of tran- tection techniques become necessary. sistors would effect the savings. At an early point in the development of tran- However, these figures assumed in part the de- sistors for telephone circuits, Bell Laboratories velopment of a low -cost transistor which could engineers recognized a unique problem. Tran- withstand residual lightning surges without sec- sistors, which operate on very low values of ondary protection. Such a transistor has been current, may be seriously damaged by a surge developed for the E -6 repeater which is now being of voltage above their operating range. Such manufactured by the Western Electric Company. voltages may be impressed on telephone equip- The E -6 repeater is a transistorized version of ment when carbon block protectors "spark over." the present E -23, which is a combination of the The problem was solved by employing diodes as E -2 and the E -3. Comparing the E -6 and the secondary protection in conjunction with the E -23 on a component- for -component basis, we find primary protector, the carbon block. (RECORD, that each of the two vacuum tubes in the old re- July, 1958). This was a successful device and it peater is replaced in the new by four p -n -p low - represented a new departure in protection for power alloy -junction germanium transistors. The transistors of each pair are connected to each other E. J. Seng studies the hysteresis loop of a tran- in what is called a "pig-a- back" arrangement. sistor he is surge- testing for the new E -6 repeater. On first thought it may seem that using four

July 1961 251

www.americanradiohistory.com times the number of transistors as the number of posure and measured surge voltages. On the basis tubes is incompatible with the goal of economy. of the experimental data they devised a surge This is not the case. In fact, early exploratory test circuit which simulated the worst conditions work had shown that gain in electrical current of lightning exposure. With this test circuit en- requirements in these transistors could be relaxed gineers could study in the laboratory the reaction with the pig -a -back arrangement. of a particular transistor junction to a residual Precisely, designers computed the compound lightning surge. gain (mathematically represented as alpha) for Testing was begun on a number of transistors the pig -a -back arrangement. This gain depends on having different mechanical, chemical and elec- the individual gain (alpha requirement) for each trical properties. The extent of damage to any transistor. The computations showed clearly that unit was determined by comparing its electrical a decrease of ten per cent in the alpha require- characteristics after testing to its original char- ment of each transistor resulted in a decrease of acteristics. The change in these characteristics only one per cent in the value of alpha for the cir- was the measure of the transistor's susceptibility cuit. A further benefit derived from using tran- to lightning surges. Of the group originally sistors is that all parameters of alpha change- tested none was completely unaffected by surges, time, temperature, variations in manufacture, for although some transistors were less susceptible example- become less significant. than others. However, the degradation and ultimate electrical collapse of many of the Different Transistor Characteristics Resolved transistors was so catastrophic that engineers assumed severe mechanical damage to the tran- Another problem resolved during early devel- sistor had occurred. opment models of concerned the fact that early Examination of these transistors under a the E -6 repeater used three types of transistors, microscope proved this. Nearly all units that divided according marked in char- to differences failed revealed a filament -like growth of indium acteristics. But as the E -6 developed, changes in which formed radially outward across the junc- led in re- circuit design to changes transistor tion from the indium electrode. If a transistor quirements, until all transistors were the same was subjected to further pulsation after it had type. The Western Electric Company was then failed, the filament grew until it was visible to manufacturing Type 12 the transistor which was the naked eye. electrically and mechanically compatible with the The mechanism behind the formation of this requirements for the E -6 repeater. However, filament is a peculiar and interesting phenomenon little was known about the susceptibility of the and may be worthy of investigation in itself. Type 12 to lightning surges. Indeed, as we will show later, speculation on its With this background, studies began that led to causes had tangible results in design technology the development of a self -protecting transistor. The project was, incidentally, an excellent illustra- PEAK PULSE VOLTS tion of how different areas of development at Bell 50 Laboratories often support each other. For while basic studies on transistors exposed to lightning 45 were conducted at the Allentown Laboratories, 40 engineers at the Murray Hill and Merrimack Val- ley Laboratories who designed the repeater cir- 35 cuit made changes in the circuit configuration 30 that eased the requirements for any single tran- 25 sistor and therefore made the general development problem easier. 20

The primary development problem was two- 15 fold : first, to investigate the susceptibility of p -n -p alloy junction transistors to residual surges 10 of lightning, and second, to ascertain the design factors that give a transistor resistance to these surges. The first practical step was to analyze 0 1 2 3 4 5 6 7 8 910 15 20 25 the environment of the transistors during light- NUMBER OF REVERSE PULSES ning exposure. Curves show the alteration of saturation current, To do this, Laboratories engineers studied the an important measure of an alloy transistor's elec- circuit of the experimental repeater during ex- trical stability, in four surge- tested transistors.

252 Bell Laboratories Record

www.americanradiohistory.com for the transistor. However, the main line of investigation was necessarily directed toward the discovery of methods to control the phenomenon rather than toward research on its causes. A promising step toward this control was taken through a redesign of the repeater circuit. Engineers at Merrimack Valley had studied closely the environment of the repeater circuit when subjected to lightning surges. They found that the greatest energy component of a particular surge was invariably directed to one transistor in the circuit. On this basis circuit requirements were changed to redistribute foreign potentials. This, in effect, reduced the energy content of a typical surge under the worst conditions. Transistors were then tested under the new surge conditions. As before, they failed; but OLLECTOR ELECTRODE with one significant difference. Units that failed under the new test conditions did not exhibit a visible filament. It is believed, however, that the cause was the same, the difference being that transistors tested under less intense surges developed filaments too small to be detected. INDIUM Again, the mechanics of the formation of this EMITTER ELECTRODE filament was not, nor is it yet, clearly understood, but considerable evidence supports the hypothesis The semiconductor element of a typical alloy - that it may be the same mechanism governing junction transistor. The photograph is magnified the phenomenon of surface breakdown. approximately 30 times to show the filament (dark line, at the top) resulting from lightning surges. The electrical characteristics of a semiconductor device are to some extent influenced by surface can be assured over a long period of the condition of its surface as well as by its body time only if the device is encapsulated in a very properties (RECORD, November, 1957). For ex- dry ambient. ample, one important design parameter is the To preclude any changes in the surface con- collector breakdown voltage -the voltage at which dition of the transistors for the E -6 repeater, the collector current suddenly increases when a a moisture "getter" (a glass sponge) was included negative potential is applied to the collector. It in the capsule. Reliability studies conducted at was noticed that the breakdown characteristics the Laboratories on devices encapsulated in this of a transistor were more sensitive to change as manner indicated excellent prospects for a long a result of surge testing than were its other service life for these transistors. characteristics. Moreover, of all design factors To confirm this, six final preproduction models which affect breakdown characteristics of a of the E -6 repeater were installed and used for surge- tested transistor, surface treatment shows a year at both terminal and intermediate loca- the most influence. Apparently a transistor's tions. Lightning surge recorders were installed susceptibility to surges varies with its surface with the repeaters. At the end of the year the conditions. Optimum surface conditions are vital repeaters were taken to the Laboratories and if a transistor is to withstand surge voltages given gain and load tests. The surge data that from lightning. were recorded indicated a high exposure to light- Normally, the surfaces of semiconductor de- ning, but no repeater tested showed any appre- vices are composed of oxide layers of various ciable transistor aging. degrees and purity. To realize optimum surface In brief, the transistor developed for the E -6 conditions these layers must be stabilized. This repeater combined the ability to meet the elec- requires the application of a chemical oxide to trical requirements of the repeater with re- the surface under carefully controlled conditions. sistance to lightning surges, stability during However, because oxide surfaces are very sensi- long -term service and the capability of low -cost tive to moisture, the stability of the "built -in" manufacture.

July 1961 253

www.americanradiohistory.com Training Simulator For Flight Controllers

To meet the communication demands resulting from the tremendous increase in air traffic and faster aircraft, Bell Laboratories designed and developed the No. 300 Switching System for air route traffic control centers. This system provides voice -communication facilities within a control center as well as fast access to lines to participating agencies concerned with flying operations (see RECORD, May, 1961) . To train a controller to operate the equipment for this new system, A.T. &T. requested Labora- tories' engineers to design a training simulator. F. W. Monsees points out various types of This unit simulates the basic operating features Author keys on the simulator for the No. 300 System. of the console for the No. 300 Switching System, with provision for control by an instructor. The simulator consists of three basic parts : an in- ing the appropriate key, the student is connected structor's console, a student's console and a to the instructor. When the student answers a cabinet containing the required relay equipment. second call, the first call is released unless it was With his console, an instructor transmits sig- placed on "hold." A call -storage feature indicates nals to a student and monitors his responses. waiting calls by a "supervisory" lamp which For signaling, there are three -position lever -type continues to flash even when a call is answered. keys, both locking and nonlocking. A lamp asso- By operating pushbutton keys, an instructor ciated with each key at the instructor's console can transmit various tone signals to the student is connected in parallel with a similar lamp in controller. These include the conventional dial the student's console. In this way, the instructor tone, busy tone, and audible ringing. There is sees all the signals he transmits to the student also a beep tone to indicate recording of a con- as well as all the signals the student originates. versation, and a tone that indicates previous A voice circuit between the two consoles permits seizure of pulsing path by another controller. the instructor to tell the student what to do under The switching apparatus is housed in a stand- certain circumstances and enables him to test the ard cabinet with a removable front. Inside the student's operating techniques. The instructor cabinet, the relay switching and power equipment can simulate and control virtually all traffic con- is mounted on a gate. The power is fed into a ditions that confront a flight controller. rectifier that provides the 48 volts needed for The keys, lamps, and pushbutton key set at the relay equipment. To avoid damage to any the student's console are identical to those on equipment, the entire apparatus (including the the regular console for the 300 system. Multi- consoles) is arranged to be inoperative until the colored designation strips indicate the various instructor plugs his headset into the proper jack. types of telephone services available to a con- The portability of the equipment, the talking troller. The student uses an "indirect- access" circuit between the instructor and student, the key to make a connection by pulsing a two- or key system, and the duplication of lamp signals three -digit code on his pushbutton key set. A at the student's console provide all that is re- "direct- access" key is used to place a call. To quired for rapid, effective training of controllers. indicate the status of various types of calls, there The simulator was designed, built, and tested are flashing, fluttering, winking, and steady lamp in 40 days. The satisfactory completion of this signals on the simulator. job is the result of close cooperation between the As soon as the student receives an incoming Federal Aviation Agency, Bell Laboratories, the call, a lamp flashes. When he answers the call, American Telephone and Telegraph Company, the lamp signal changes to flutter. The instructor and the Western Electric Company. transmits signals to the student in any combination. For example, he may cause several flashing F. W. Monsees lamp signals to appear simultaneously. By press- SPECIAL SYSTEMS ENGINEERING

254 Bell Laboratories Record

www.americanradiohistory.com One important factor underlying the recent success of key -telephone systems has been the development of new, compact generators for converting local 60 -cycle power at the customers' premises to 20 -cycle ringing power.

W. F. Kannenbei

Static Frequency- Generators For Ringing Power

From the earliest days of the telephone, there creased to 1200 rpm, and this raised the ringing has been a continuing need for a method of frequency by the same ratio -from 16% to 20 notifying the called customer that he was "wanted cps. Since then, 20 cycles has been the accepted on the telephone." Bells have long been the standard for ringing frequency. favored mode of notification. For many years There is no hard and fast rule fixing the ring- these bells, called "ringers," were actuated by an ing frequency at this rate, however, and from alternating current which the calling customer time to time limited exceptions have turned up. generated by turning a crank on the side of his In general, however, the ringing frequency and telephone cabinet. its prominent harmonics should be below the nor- The frequency of the alternating current mal transmission range of speech. Also, its trans- furnished by the magneto-electric generator to mission over telephone lines should be good, and which the crank was attached was obviously vari- this property improves as frequency decreases. able, since it depended on the speed of rotation of In the 1930's, the Bell System began to make the crank. For example, after a stimulating break- improved private branch exchanges available to fast a customer's young son could easily produce customers, as well as versatile multi -line station a frequency of 17 to 20 cycles per second. At the arrangements called "key telephone" systems. end of a hard day, the customer himself would These key systems- starting with the lA and 1A1 very likely generate less than 15 cps. -have gained widespread acceptance. The latest As time went on and mechanized telephone ex- of these, the 6A system, uses multi- button key changes came into being, ringing frequencies sets including the Call Director, and offers such were generated by a rotating machine (1000 services as conferencing, pushbutton signaling rpm) in the central office, and a standard fre- and intercom dialing (RECORD, March, 1958). quency of 16% cps was adopted. Around 1920 Key systems are of course located on the cus- or so, the operating speed of the machine was in- tomer's premises; thus supplying operating power

July 1961 255

www.americanradiohistory.com and ringing power from the central office to the BELOW 20 CPS OUTPUT OSCILLOSCOPE DISPLAY several sets that make up the system is difficult FLUX t A and expensive. Therefore, when the key systems were originally designed, small power plants suitable for installation on the customer's prem- m, ises were developed as an integral part of the MAGNETIZING system equipment. FORCE Primarily, these power plants furnish local power for talking and signaling as well as ringing B power of the proper frequency. This article de- OSCILLOSCOPE DISPLAY scribes the development of a static frequency 20 CPS OUTPUT generator -the 107 -B- designed for the latest FLUX t A version of the packaged power plant, the 101 -G. This generator has no moving parts, hence the term "static." MAGNETIZING The basic job of the frequency generator is FORCE to produce 20-cps ringing current, for local ringers and ring -down signaling in key systems, from the standard 60 -cps power available at the customer's premises. Static ringing supplies generate this 20 -cps current by using the nonlinear Top: line and inductor current (left) and hysteresis characteristic of a saturable magnetic core to loop (right) for saturable inductor (L1) in ring- convert energy from the line frequency (60 cps) ing frequency generator before 20 -cps output be- to several related frequencies. One of these re- gins. Same curves during output are shown below. lated frequencies is a subharmonic of the line frequency. By proper tuning, the desired sub - range of adjustment of the tuning elements. harmonic (20 cps) can be selected. Messrs. J. M. Since correct tuning involves an inductance Manley, E. Peterson, L. R. Wrathall and others value for the saturable inductor that is a function at the Laboratories explained this phenomenon of its degree of saturation, the circuit will not some years ago and proposed basic circuits. Com- behave normally when the degree of saturation is mercial designs of the circuit were developed too low. Thus, this circuit will not produce ring- by the Power Apparatus Department. ing current at an input voltage below the operat- To explain the principle of operation briefly ing region. This fact lets us demonstrate how the and simply, let us consider the equivalent circuit circuit works in its operating region. of the generator. This circuit has two meshes The line current at fl and the current in the with a common element. Mesh 1 comprises a sat- saturable inductor, for an input voltage below the urable inductor and a tuning capacitor. Mesh 2 threshold at which the circuit will start to "work." comprises the same saturable inductor, the power are shown in the diagrams above. Line current in source, a fixed inductor and a tuning capacitor. the upper left diagram is virtually sinusoidal and Operating conditions require that network im- inductor current shows a "pip" at each succeed- pedances be adjusted so that two sinusoidal coming half cycle. (These illustrations contain six ponents besides the applied current are allowed complete wavelengths at 60 cps. The pips alternate to flow through the saturable inductor. This pro- and occur once each half cycle.) duces oscillations at two separate frequencies, f2 At a slightly higher input voltage, the circuit and f3. The sum of frequencies f2 and f3 is equal works in the "normal" manner, that is, it pro- to twice the applied frequency, f1. duces the desired 20 cps. The current wave- For this circuit, fl, f2 and f3 are, respectively, form immediately below shows what has happened 60, 20 and 100 cps. Thus, Mesh 1 is tuned to 100 to both line current and inductor current. The cps, and Mesh 2 is tuned to 20 cps. The inductance line current is no longer sinusoidal, but its pat- of the saturable inductor is not constant, however, tern shows one repetition in three full 60 -cps so the two circuits are tuned correctly only for waves. In other words, the line -current pattern that value of inductance corresponding to its de- repeats at a 20 -cps rate. gree of magnetic -core saturation in the working The inductor, or coil, current also shows some circuit. Fortunately, the tuning of these circuit revealing changes. Every third pip is highly ex- meshes is broad, and the circuit functions over a aggerated, while the two intervening pips are

256 Bell Laboratories Record

www.americanradiohistory.com much lower than those above, even though the nonpolarized input. Both requirements can be met 60 -cps input voltage is higher. It is convenient by using transformers. The actual circuit of the to think of this as an accurate counting operation. 107 -B generator is shown on this page. Idealized hysteresis loops of the saturable in- Physically, the new frequency generator is ductor show that this counting mechanism is small and compact, and as mentioned earlier, is a related to the flux changes during each period of component part of the 101 -G power plant. It has the 60 -cps input. Typical hysteresis loops cor- two output terminals, and the flexible input con- responding to the current and voltage curves are nection can be readily plugged into any standard shown on the right in the diagrams. 117 -volt, 60 -cycle outlet on the customer's prem- In the upper -right loop, a very small change ises. In service, it is designed to ring eight aver- in flux results from a large change in magnetizing age high- impedance (B -1 -A) ringers without force, indicating that the penetration into satura- capacitors, two such ringers with capacitors at tion at points A and B is slight and is repeated 75 volts or over, or six ringers with capacitors at twice each cycle. In the lower -right loop, this 60 volts or above. A modified version of the 107B penetration into saturation is very deep, and oc- generator (coded 107C) will ring eight such ring- curs only twice in three cycles of the input. These ers without capacitors or six ringers with capaci- hysteresis loops have been somewhat distorted to tors at a voltage of 75 or above. show more clearly the nature of successive loops. An important advantage of the new circuit design is "paralleling." That is, if more load - Counting Operation carrying capacity than that furnished by a single The counting operation may be visualized from generator is required, it is possible to connect this loop display. From saturation at point A, the in parallel as many generators as are needed. The flux change in the first half cycle of the input only qualification is that all input and output frequency is only sufficient to bring the flux to leads be poled alike. Only generators of the same point B, which is short of saturation. In the sec- code can be operated this way, however. ond half -cycle, the flux changes in the opposite Static ringing- frequency generators are small, direction to point C. In the third half- cycle, the light -weight and easy to install. They are low - flux once again goes to saturation at point D. Dur- cost, have no moving parts or electron tubes, and ing the next three half -cycles, the flux changes require no maintenance. At current production similarly to points E, F and A successively. To rates of over 1000 units per week, they lend effec- change the flux from its value at point A, through tive support to the Bell System's merchandising these six steps and return to point A, requires efforts on multi -button key systems. three complete cycles of the input frequency. The wave shape of coil current shown at the o lower left is a powerful source of odd harmonics. And since two sets of alternating "spikes" are shown within the time span of six 60 -cps waves, the spike pattern must be occurring at a 20 -cps rate. Accordingly, all odd harmonics of 20 cps are being produced. The circuit meshes are therefore a tuned to approximately 20 and 100 cps, so that the 20 -cycle "fundamental" and the fifth harmonic

1 100 cps) components will be the most prominent in their corresponding circuit meshes. Since the capacitive reactance of the tuning capacitor in the first diagram varies inversely with frequency, the voltage drop across this capacitor will be chiefly 20 cps, with the third and fifth harmonics present at correspondingly reduced amplitude. A 20 -cps output suitable for ringing power can then be taken off at this capacitor. In an actual generator circuit, the circuit elements should be used near their full ratings in Circuit of the 107 -B generator. Transformers T1 the interest of economy and good design. Also, and T2 are used in the commercial circuit. 20 -cps the 20 -cycle output should be isolated from the output is taken off a winding on T2, at the right.

July 1961 257

www.americanradiohistory.com In a recent lecture at the American Iron and Steel Institute, Dr. J. B. Fisk said methods the Laboratories developed to achieve reliability in ocean cables will be applicable in the field of satellite communications.

Sapphires To Protect Telephone Satellites From Space Hazards

Thousands of pieces of man -made sapphire will the satellite and used to recharge a battery which, cover the surface of the communications satellites in turn, is a continuous source of power. now being developed by Bell Telephone Labora- Because they are exposed on the surface of tories. The sapphires are expected to protect solar the satellite, the solar cells are vulnerable to cells from space radiation, enabling "working" radiation damage, particularly electron bombard- telephone satellites to endure the rigors of space ment and proton bombardment. The sapphire for 10 years or more. sheathings will protect the solar cells from the Dr. J. B. Fisk, President of Bell Laboratories, deteriorating effect of these bombardments, and, delivering the fifteenth annual Charles M. Schwab at the same time, will admit light to the solar Memorial Lecture to the American Iron and Steel cells. Institute, cited the sapphire protection as an ex- Two different sizes of satellites are being con- ample of the thorough -going measures that are sidered, Dr. Fisk said. One will be 27 inches in being taken to achieve long -life diameter, the other, four feet. Each, roughly News of reliability for satellites. spherical in shape, may have as many as 60 Satellite As an old hand at problems of gem -like facets. These facets will equalize the Development reliability, the Laboratories is amount of light falling on each solar cell. More using an approach it evolved in developing sub- than half the surface of the smaller satellite will marine cable systems. With these exacting be covered by over 4000 solar cells; the larger methods, Dr. Fisk said, the Laboratories devel- one, by 12,000 cells. Each cell will be covered by oped a submarine cable system that has an a slice of the man made, crystal -clear sapphire. expected life length of 20 years or more. Some Other protective materials-high -quality glass, 1500 electron tubes have functioned under the or high -quality quartz, for example -are being oceans for the past two to six years without a considered, but sapphire appears most promising. failure. It does not cost significantly more than other The methods developed for the cable system materials (it is only about one third of the cost are now being applied to satellites. "The result," of the solar cells themselves) and it has other said Dr. Fisk, "should be a shipshape, space - advantages. For one, it will convey heat away, worthy communications relay station." preventing the solar cells from being overheated The Bell System has previously announced in long periods of continuous sunlight. plans to develop a satellite communication sys- Another advantage is that the use of sapphire tem and put it into operation as soon as possible. helps solve a problem involved with thermal ex- A ground station in Maine will be ready early pansion. In space, changes of temperature on the next year. The first test satellite will be ready surface of the satellite will be rapid and extreme, at the same time if the government designates a possibly hundreds of degrees in a few minutes. launching vehicle soon. The Bell System has With a few exceptions, all substances undergo a offered to pay costs of the rocket and launching. change of dimensions when they are heated. One big problem in operating a radio receiver However, this change, or expansion, occurs at and transmitter in space is the source of elec- differing rates for different substances and some trical power. At present the solar cell, a Labora- substances will expand more than others. tories invention which converts light from the If the difference in expansion is too great be- sun directly into electricity, is used. Thousands tween two materials which are fastened together, of these cells will be placed on the surface of they will separate. Therefore, the thermal char-

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www.americanradiohistory.com acteristics of the sapphire should match those of the materials used to fasten it to the satellite. On the experimental satellite, the sapphire slices will be brazed to platinum sidebars which will be soldered to a special ceramic base. These materials all expand at very nearly the same rate. Dr. Fisk pointed out another unique and interesting problem -the antenna. The experimental satellite antenna will receive signals from the ground, and, after they are amplified and changed to a new frequency, transmit them again. The satellite being developed at the Laboratories will use an equatorial antenna; its opening will be a eares slot around the middle of the satellite. (See b i photograph on this page.) ) 4 it This antenna radiates energy in all directions. 419 memo It poses a problem in that only a small fraction of ma al mmr( this energy reaches the ground. Although even 1`%, I, s s. . I- this fraction will be sufficient for the extremely R. J. Nielsen sets into place an assembly of solar low -noise ground receivers developed at the cells with a transparent covering of sapphires. Laboratories, if the antenna could be always pointed at the earth we would have a more efficient receiving and transmitting system. structure will provide the necessary rigidity and, Bell Laboratories engineers have proposed at the same time, will be relatively light weight methods of doing this that involve sensing the to facilitate the antenna rotation. direction of the earth by magnetic field or horizon To protect the antenna from adverse weather detection. Other methods would employ various conditions a radome, which Dr. Fisk described, kinds of motors or jets to turn the antenna. One is being built. A basic requirement of the mate- interesting idea "lets nature do the job." rial to be used for this structure is that it be Two equally weighted objects, connected to- transparent to radio energy. Dr. Fisk said that gether like a dumbbell, would be put in orbit, one we plan to construct a radome of synthetic rub- end nearer the earth than the other. Because of ber and plastic which will be the largest inflated tàe pull of gravity on the closer object, the structure yet built. It will be a 20 -ton structure, dumbbell would point toward the earth and sweep 161 feet high and 210 feet across and would cover through its orbit in that attitude. The closer of three acres if it were laid out flat. the two parts of the dumbbell would always show The first experimental satellite will help fill the same face to the earth. The antenna would the pressing need for a real life -test in space. It be placed in that face. will serve to life -test the components planned for a working satellite system and also to gain more Ground Station Progress precise information on the environment of outer Work is also proceeding rapidly on ground space. For example, it will be used to take more stations, Dr. Fisk noted. At Rumford, Maine a precise measurements of the exact amounts of horn- reflector antenna is being constructed which radiation in the Van Allen belts at various alti- is three times as large as the one used for the tudes and under varying circumstances. original Echo experiments at Holmdel. This Dr. Fisk recalled that at the time of the first antenna will be a 250 -ton steel and aluminum Echo experiment, less than a year ago, satellite rotating structure, 177 feet long and 94 feet communication work "was considered research." high. Used for both transmitting and receiving, However, progress has been so rapid that the it will transmit signals to a satellite and receive Laboratories is now principally concerned with signals relayed by the satellite from overseas. evaluating possible alternative methods for best The shape of this antenna must be maintained handling various aspects of a satellite system. very precisely no matter which way it points so "Satellite communications," he said, "has now that it will not miss the tiny satellite some 7000 moved into the field of systems planning and miles away. Thus, the horn must be extremely development, although research continues in the stiff. The broad surfaces of the horn will be never-ending effort to find new principles and made of alnniinuni with a honeycomb core. This methods for the long -range future."

July 1961 259

www.americanradiohistory.com SERVICE QUICKLY RESTORED AFTER REPEATER STATION BLASTS

Early Sunday morning, May 28, the TD -2 done. This installation was completed by June 4. repeater stations at Wendover, Nevada and Cedar Permanent restoration is expected to be completed Mountain, Utah, and the K repeater station at at all three locations before September 1. Knolls, Utah, were blown up and virtually de- As a precautionary measure, National Guards- stroyed, interrupting both the central transcon- men had been posted quickly at all unattended K- tinental microwave and K- carrier routes. More carrier and radio -repeater stations in the area. than 2200 telephone and telegraph circuits and They were replaced by Bell System guards a few four television channels were interrupted. days later. Many normally unattended stations in Two thirds of the telephone circuits, all crit- Utah, Nevada and California are continuing to be ical services and all TV and attended or guarded. News of radio circuits were made good by the Bell rerouting within a few hours System after the blasts. The radio systems were rerouted around the damaged section by way of Los Angeles within two hours. By Sunday evening all circuits affected by the explosions had been made good, using spare facilities and protection radio channels. Pre -arranged emergency service restoration plans worked smoothly. In less than 30 minutes after word was received, men and materials were moving to the three stations. Portable microwave equipment and truck -mounted towers were flown to the two radio relay locations. Despite the high number of circuits blanked out, the effect on traffic was light. Many military private line circuits were not affected at any time by the explosions because of alternate routings. Also, many other private line circuits were indi- vidually rerouted with minimum delays. One two -way TD -2 channel was made available between Salt Lake City Junction and Los Angeles Tuesday night, May 30, by expediting installation of new channels that were nearing completion. This released some of the protection channels that had been used for reroutes. Portable TE Microwave equipment was brought in to restore service across the breaks. By June 2 four TE channels had been set up, two for message service, one for TV, and one for protection. Five K -1 systems were restored by cutting the cable through at Knolls and using additional amplifiers at the adjacent stations. Temporary buildings have been constructed at the three sites, and a temporary installation of TD -2 equipment has been made at the two radio sites to serve until permanent rebuilding can be A view of a typical TD -2 microwave relay station.

260 Bell Laboratories Record

www.americanradiohistory.com W. O. Baker To Serve On President's Board news in brief W. O. Baker, Laboratories Vice President, Research, was recently J selected by President Kennedy to serve on the re- established Presi- New Instrument Measures Punching Pressure dent's Foreign Intelligence Ad- The Board was Paper perforator tape is used forator tape. With this instru- visory Board. organized in 1956 by former in large quantities in the Bell Sys- ment, engineers can determine Eisenhower "to con- tem to record and transmit infor- whether various tapes can he per- President duct independent review of the mation by teletypewriter. The forated at a certain pressure to foreign intelligence and related accuracy of such information de- produce a uniformly clean hole. activities of the government." pends in a large measure on the Because tapes have specific pres- Baker also served on the of the sure requirements, this instru- Mr. "punching characteristics" the Eisenhower ad- ment should be an important tool Board during paper. Recently, the Chemical Re- ministration. search Department devised an in- in providing a fast, accurate check strument that measures pressure on one of the characteristics of required to punch a hole in per- teletypewriter paper. Columbia University Chair Named for Former Chemical Director A Robert R. Williams chair, named in honor of the former Chemical Director of Bell Lab- oratories, has been established at Columbia University. Endowed by a $500,000 fund from the Re- search Corporation of New York, the chair is established in the Institute of Nutrition Sciences, part of Columbia's School of Pub- lic Health and Administrative Medicine. Mr. Williams, who is best known publicly for his work in first synthesizing Vitamin B -1, also made important contributions to industrial chemistry during more than 20 years' service with the Laboratories. He retired in 1946. To mark the creation of the Columbia Chair and to honor Mr. Williams, 200 public health lead- ers and business officials gathered at a dinner in New York recently.

A.T.BT. Will Have Biggest Industrial Exhibit At World's Fair A.T. &T. last month contracted to become the largest single ex- hibitor in the industrial section of the 1964 -1965 New York World's Fair. A.T. &T. signed a lease for a 105,000- square -foot site on which the Bell System will begin construction of the exhibit building next spring. Henry Dreyfus, the noted designer, and the archi- D. J. Nitti with i 1, ,1 1n aiems arc paper tape punching pres.r, tectural firm of Harrison &

July 1961 261

www.americanradiohistory.com news in brief (CONTINUED)

Abramovitz, noted for its work on B. McMILLAN TAKES AIR FORCE POST the U. N. Building and other large projects, will collaborate on the building and the exhibit. The exhibit will feature the latest communications services and a look into the future.

Two from Laboratories Honored by NAS The National Academy of Sci- ences recently elected to member- ship W. O. Baker, Vice President, Research, of the Laboratories and J. W. Tukey, Assistant Director of Research -Communications Principles. The Academy was established in 1863 as a private, non -profit organization of scientists to advance science and ad- vise the government on scientific and technical matters. Among its Laboratories members are Dr. J. B. Fisk, H. W. Bode, J. R. Pierce, W. H. Brattain and three retired presidents of the Laboratories, Dr. M. J. Kelly, the late Dr. O. E. Buckley, and the late Dr. F. B. Jewett.

Two Universities Honor J. R. Pierce Two honorary degrees were awarded in June to John R. Pierce, Brockway McMillan, at left, is sworn in as Assistant Secretary of Bell Laboratories Director of Re- the Air Force by Air Force Secretary Eugene M. Zuckert. search- Communication Principles. Northwestern University be- stowed an honoray Doctor of Brockway McMillan, Director has been associated with the Of- Science degree on Mr. Pierce, cit- of Military Research since 1959, fice of the Special Assistant to ing him as an "electrical engineer has resigned from the Labora- the President for Science and of international distinction," and tories to accept an appointment Technology, the Office of the As- lauding him for his work in the as Assistant Secretary of the Air sistant Secretary of Defense for development of the Echo satellite. Force for Research and Develop- Research and Development, the The citation also called to atten- ment. Mr. McMillan joined the Office of Defense Mobilization, tion his many books and articles Laboratories in 1946 as a research and the Weapons System Evalua- as evidence of his professional mathematician. He became As- tion Group of the Joint Chiefs of standing. sistant Director of Systems Engi- Staff. He is a graduate of the At a ceremony in Newark, N. J., neering in 1955 and four years Massachusetts Institute of Tech- the Newark College of Engineer- later was named Director of Mili- nology having earned a Bachelor ing awarded the Doctor of Engi- tary Research. His work in statis- of Science degree there in 1936 neering Degree to Mr. Pierce. He tics and communications theory and a Ph.D. in mathematics in was cited for his work as a re- has won six patents on computing 1939. He served for several years search scientist in developing the devices and amplifier circuits. Mr. as an instructor at M.I.T. and at beam traveling -wave tube and in McMillan has previously served Princeton University before go- originating the concept of satel- the government as a consultant or ing on active duty with the U. S. lite communications. member of various agencies. He Navy in 1943.

262 Bell Laboratories Record

www.americanradiohistory.com PAPERS

Following is a list of the authors , titles and places of publica- Kuebler, N. A., see Nelson, L. S. Lion of recent papers published by members of the Laboratories. Kurpis, G. P., Directional Channel Separation Filters, Northeast- Barnes, W. C., Band Elimination 32, pp. 27S-34S, Mar., 1961; ern University Library. Filter Employing Quartz Crys- Electronics, 34, pp. 61 -67, May Labuda, E. F., and LeCraw, R. C., tal Units, Thesis, Northwestern 5, 1961. New Technique for Measure- University Library. Gibbons, D. F., On the Observa- ment of Microwave Dielectric Barrett, W. A., Demagnetization tion of de Haas -van Alphen Constants, Rev. Sci. Instru., of Twistor Bits, J. Appl. Phys., Type Oscillations in the Acous- 32, pp. 391 -392, Apr., 1961. 32S, pp. 35S -36S, Mar., 1961. tomagnetic Attenuation of Zinc, LeCraw, R. C., see Labuda, D. F. Bennett, W. R., and Froehlich, Phil. Mag., VI, pp. 445 -448, Lewis, J. A., Generalized Thermal F. E., Some Results on the Ef- Jan., 1961. Resistance, Quart. Appl. Math., fectiveness of Error -Control Gilbert, E. N., Design of Mixed 19, pp. 76 -89, Apr., 1961. Procedures in Digital Data Doubles Tournaments, Am. Lewis, J. A., and Pollak, H. O., Transmission, Trans. I.R.E., Math. Monthly, 68, pp. 124 -131, Photoelastic Calculations by a CS -9, pp. 58-65, Mar., 1961. Feb., 1961. Complex Variable Method, Bogert, B. P., see Kramer, H. P. Gordon, E. I., see Buchsbaum, Zeitschrift für Angewandte Brown, S. C., see Buchsbaum, S. J. S. J. Mathematik and Physik, XII, Buchsbaum, S. J., Gordon, E. L, Gordon, J. P., see Yariv, A. pp. 30 -37, 1961. and Brown, S. C., Experimental Gray, M. C., Bessel Functions of Logan, R. A., see Trumbore, F. A. Study of Plasma Column in a Integral Order and Complex McSkimin, H. J., Effect of Diffrac- Microwave Cavity, J. Nucl. Argument, Communications of tion on Velocity of Sound, J. Energy, Part C: Plasma Phys- the A.C.M., 4, p. 169, Apr., 1961. Acous. Soc. Am., 33, p. 539, ics, 2, pp. 164 -168, 1961. Grubbs, W. J., A Unidirectional Apr., 1961. Bugnolo, D. S., Stochastic Proc- Amplifier with Esaki Diodes, Meitzler, A. H., Mode Coupling esses and Beyond- the -Horizon Trans. I.R.E., ED -8, pp. 163- Occurring in the Propagation Propagation, Trans. I.R.E., 169, Mar., 1961. of Elastic Pulses in Wires, J. AP -9, pp. 226 -227, Mar., 1961. Guldner, W. G., A Review of the Acous. Soc. Am., 33, pp. 435- Burgiel, J. C., Jaccarino, V., and Determination of Oxygen, Hy- 445, Apr., 1961. Schawlow, A. L., Nuclear Quad- drogen, Nitrogen and Carbon Meitzler, A. H., Ultrasonics. Part rupole Resonance in an Anti- in Metals, Talanta, 8, pp. 191- 1: Principles of Ultrasonics, f erromagnet, Phys. Rev., 122, 202, Apr., 1961. Part 2: Application of Ultra- pp. 429 -436, Apr. 15, 1961. Hagelbarger, D. W., sae Kramer, sonics, International Corre- Denton, R. T., Theoretical and H. P. spondence Schools, 1961. Experimental Characteristics of Harmon, L. D., see van Bergeijk, Merritt, F. R., see Galt, J. K. a Ferromagnetic Amplifier Us- W. A. Murphy, R. B., On the Meaning of ing Longitudinal Pumping, J. Jaccarino, V., NMR and the Con - Precision and Accuracy, Mate- Appl. Phys., 32, pp. 3005 -3075, duction Electron Polarization. in rials Res. & Standards, 1, pp. Mar., 1961. Rare Earth Metals, J. Appl. 264 -267, Apr., 1961. Dillon, J. F., Jr., A New Charac- Phys.-Proc. Conf. on Magnet- Nelson, L. S., and Kuebler, N. A., teristic in the Temperature De- ism, 32, pp. 1025-1065, Mar., Heterogeneous Flash Pyrolysis pendence of Ferrimagnetic Res- 1961. of Hydrocarbon Polymers, Proc. onance Line Width in Some Jaccarino, V., see Burgiel, J. C. Conf. on Phys. Chem. in Aero- Rare Earth Doped Yttrium Jenkins, H. M., The Effect of Dis- dynamics & Space Flight, pp. Iron Garnets, J. Appl. Phys.- crimination Training on Ex- 61 -67, 1961. Proc. Conf. on Magnetism, 32, tinction, J. Experimental Psy- Nesbitt, E. A., Williams, H. J., pp. 1595 -1605, Mar., 1961. chology, 61, pp. 111 -121, Feb., Wernick, J. H., and Sherwood, Freeland, P. E., see Trumbore, 1961. R. C., Magnetic Moments of F. A. Koehler, D. C., Four New Ran- Compounds of Cobalt with Rare Froehlich, F. E., see Bennett, dom- Access Memories for Digi- Earth Elements Having a W. R. tal Work, Product Engg., pp. Cu,Ca Structure, J. Appl. Phys., Fuller, C. S., Kinetics of Donor 51 -54, May 1, 1961. 32, pp. 3425 -3435, Mar., 1961. Reactions in Oxygen -Doped Kramer, H. P., Bogert, B. P., and Pappalardo, R., Cubic Field Split- Germanium, The Phys. & Chem. Hagelbarger, D. W., Stability ting and Cubic Symmetry of Solids, 19, pp. 18 -28, Apr., of Pressure Supported Molten Orthonormal Sets of Wave - 1961. Zones in Horizontal Sheets, J. Functions for J- Manifolds (J Gianola, U. F., Possibilities of All - Appl. Phys., 32, pp. 764 -763, Half -Integer), J. Chem. Phys., Magnetic Logic, J. Appl. Phys., May, 1961. 34, pp. 1380 -1388, Apr., 1961.

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Peter, M., see Sugano, S. A.C.M., 4, pp. 172 -173, 175, van Bergeijk, W. A., and Harmon, Pierce, J. R., Some Practical Apr., 1961. L. D., What Good Are Artificial Problems of Satellite Communi- Sherwood, R. C., see Nesbitt, E. A. Neurons? Bionics Symposium, Wright Air Development Div., cation, Astronautics, 6, pp. 34- Spitzer, W. G., Wernick, J. H., 60 -600, pp. 395 -406, Dec., 1960. 35, 90, 92, 94, 96, May, 1961. and Wolfe, R., Electrical and Walsh, W. M., The Effects of Hy- Pollak, H. O., see Lewis, J. A. Optical Properties of CdSnAs,, drostatic Pressure on the Para - Reed, E. D., Diode Parametric Solid State Electronics, 2, pp. magnetic Remittance Spectra of Amplifiers: Principles and Ex- 96 -99, Mar., 1961. Several Iron Group Ions in periments II; Semicon- -Part Sugano, S., and Peter, M., The Ef- Cubic Crystals, Phys. Rev., 122, ductor Products Mag. 4, pp. 35- fect of Configuration Mixing pp. 762 -771, May 1, 1961. 42, Feb., 1961. and Covalency on the Energy Wernick, J. H., see Nesbitt, E. A. Geschwind, S. Remeika, J. P., see Spectrum of Ruby, Phys. Rev., Wernick, J. H., see Spitzer, W. G. Sanders, R. W., A Crystal -Tunnel 122, pp. 381 -386, Apr. 15, 1961. Williams, H. J., see Nesbitt, E. A. Diode Oscillator, Northeastern Trumbore, F. A., Freeland, P. E., Wolfe, R., see Spitzer, W. G. Mar. 20, University Library, and Logan, R. A., Distribution Yariv, A., and Gordon, J. P., Ex- 1961. Coefficient of Antimoni, in Sili- perimental Procedures for the Schawlow, A. L., see Burgiel, J. C. con from Solvent Evaporation Determination of the Number Schmidt, P. H., see Merritt, F. R. Experiments, J. Electrochem. of Paramagnetic Centers, Rev. Sherman, P. M., Table Look -At Soc., 108, pp. 458 -460, May, Sci. Instr., 32, pp. 462 -463, Techniques, Communications of 1961. Apr., 1961. PATENTS

Following is a list of the inven tors, titles and patent numbers Moore, E. F.- Sorting Method of patents recently issued to members of the Laboratories. and Apparatus- 2,983,904. O'Brien, J. A.-Pulse Monitoring Becker, F. K. - Nonlinear Inte- Hysko, J. L., see Gardner, L. A. Circuit- 2,984,789. grating Control Circuit- 2,982,- Jaeger, R. P.- Negative Resist- Ostendorf, B. Jr., see Cadden, 885. ance Oscillator- 2,986,724. W. J. Blecher, F. H. - Prevention of Jamison, H. M. - Insertion of Pearson, G. L.- Scmiconductive Overload Instability in Condi- Fronting Information in Pulse Device- 2,983,854. tionally Stable Circuits- 2,986,- Modulation Systems- 2,984,706. Priebe, H. F. Jr. - Transistor 707. Kalnins, I. L. Process for Etch- Waveform Generator- 2,983; Blount, F. E. - Fast Response ing a Glass -Containing Surface 878. Gating Circuit- 2,985,769. -2,982,626. Prim, R. C., see Darwin G. P. I. M. Electroluminescent Bobeck, A. H.- Magnetic Trans- Kamps, P. J. -High Leakage Re- Ross, - lating Circuit- 2,985,768. sistance Electromagnetic Relay Switching Apparatus - 2,984,- 749. W. J. Translator -2,985,733. Cadden, -Code St. John, G. E. -Low -Noise Elec- -2,982,953. Ketchledge, R. W. Pulse Length Controlled Servo System-2,- tron Gun- 2,985,789. Cagle, W. B. Semiconductor - 985,808. Sauer, H. A. Controlled Atmos- Trigger Circuit- 2,982,869. Matthias, B. T.-Monoclinic Gly- phere Cabinet- 2,985,497. Modu- Chasek, N. E.- Frequency cine Sulfate and Isomorphs- Sullivan, M. V. - Treatment of lation Reception Circuits -2; 2,986,681. Senticonduct i v e Bodies -2,983; 984,791. Maurushat, J. Jr. - Alarm and 655. Darwin, G. P.- Synchronization Test Equipment for Carrier Terry, N. S.- Automatic Deter- in a System of Interconnected Systems- 2,986,610. mination of Toll Call Charges Units-2,986,723. May, J. E. Delay Line- 2,982,- -2,984,704. Gardner, L. A. - Carrier Tele- 926. Vroom, E., see Terry, N. S. graph Switchboard Supervisory McKim, B. - Dial Telephone Of- Wegel, R. L. -Wave Translating Systems- 2,985,717. fice Arranged for Resistersend- Systems- 2,982,924. Godfrey, J.- Fabrication of Semi- er Control of Two- Motion Step - Wick, R. F., see Wegel, R. L. conductor Devices- 2,984,897. by -Step Switches Having Multi- Wilson, R. L., see Jamison, H. M. Herriott, D. R. Modified Optical level Trunk Groups- 2,986,604. Wolfe, R. M. - Electrical Circuit System for Off -Axis Flying - Meacham, L. A.- Telephone Sig- Employing a Ferroelectric Spot Scanners -2,984,750. naling Apparatus- 2,986,603. Capacitor-2,984,754.

264 Bell Laboratories Record

www.americanradiohistory.com TALKS

Following is a list of speakers, titles and places of presentation Solids and Liquids, Phillips for recent talks presented by members of Bell Laboratories. University, Enid, Okla. ; Phillips Petroleum Co., Bartlesville, Okla. ACOUSTICAL SOCIETY OF AMER- Meitzler, A. H., Attenuation of Ahearn, A. J., Solid State Mass ICA MEETING, Philadelphia, Pa. High Frequency Elastic Modes Spectroscopy, General Motors Bateman, T., see Mason, W. P. of Propagation in Strips of Spectrographic Committee Bateman, T. B., see McSkimin, Polycrystalline Metals. Conf., Warren, Mich. H. J. Miller, J. E., see Mathews, M. V. Alexander, S., Exchange Nar- David, E. E., Jr., see Flanagan, Pfafflin, S. M., Simultaneous vs. rowed Line Shape, Harvard J. L. Successive Observation Inter- University, Cambridge, Mass. David, E. E., Jr., see Lochbaum, vals in Signal Detection. Babington, W., Clitherow, W. R., C. C. Watson, B. J., see Flanagan, J. L. and Miller, E. E., Meeting the David, E. E., Jr., see Mathews, Challenge of High Reliability, M. V. AMERICAN PHYSICAL SOCIETY Am. Foundrymen's Soc., San Dunn, H. K., Methods of Measur- MEETING, Washington, D. C. Francisco, Calif. ing Speech Formant Band- Bozorth, R. M., Davis, D. D., and Barnes, C. E., Broadband Isola- widths. Wernick, J. H., Magnetism of tors and Variable Attenuators Flanagan, J. L., David, E. E., Jr., Dilute Solutions of Iron Group for Millimeter Wavelengths, and Watson, B. J., Binaural Elements in Platinum Metals. National Symposium, I.R.E., Lateraliza.tion of Cophasic and Buchsbaum, S. J., see Platzuran, PGMTT, Washington, D. C. Antiphasic Clicks. P. M. Barnes, C. E., A Field Displace- Flanagan, J. L., see Guttman, N. Davis, D. D., see Bozorth, R. M. ment Isolator at 57 kmc, Na- Gardner, M. B., Binaural Detec- Geller, S., Williams, H. J., and tional Symposium, I.R.E., tion of Single Frequency Sig - Sherwood, R. C., Magnetic and PGMTT, Washington, D. C. nals in the Presence of Noise. Crystallographic Study of Neo- Becker, J. A., Field Emission Mi- Gerstman, L. J., see Kelly, J. L., dymium. Substituted Yttrium croscopy, Princeton University Jr. and Gadolinium Iron Garnets. Conf., Princeton, N. J. Guttman, N., On Defining the Hensel, J. C., Effective Mass Benes, V. E., A Class of Stochas- Range of Pitch Perception. Shifts in Cyclotron Resonances tic Programming Problems, Co- Guttman, N., and Flanagan, J. L., in Uniaxially Stressed Silicon. lumbia University, Dept. of Pitch of High -Pass Filtered Kunzel, J. E., Superconductivity Statistics, N. Y. C. Periodic Pulses. in High Magnetic Fields at Bennett, W. R., Broadband Prob- Hudson, A. R., see McSkimin, High Current Densities. lems and Techniques, I.R.E. H. J. Pfann, W. G., Semiconducting 1961 Spring Lecture Series, Kelly, J. L., Jr., and Gerstman, Stress Transducers Utilizing Boston, Mass. L. J., An Artificial Talker the Transverse and Shear Pie - Bogert, B. P., Seismological Data Driven from a Phonetic Input. zoresistance Effects. Collection and Processing, Sum- Lochbaum, C. C., David, E. E., Platzman, P. M., and Buchsbaum, mit Association of Scientists, Jr., and Mathews, M. V., De- S. J., Effect of Collisions on Summit, N. J. cision Functions for Voiced - Landau Damping of Plasma Bozorth, R. M., Dilute Magnetic Unvoiced- Silence Detection. Oscillations. Solutions, Naval Ordnance Lab., Mason, W. P., McSkimin, H. J., Sherwood, R. C., see Geller, S. Washington, D. C. and Bateman, T., Third Order Sikorski, M. E., Tunnel Diode Hy- Brillinger, D. R., Asymptotic Elastic Moduli of Germanium. drostatic Pressure Transducer. Means and Variances in the k- Mathews, M. V., Miller, J. E., and Walker, L. R., The Interpretation Dimensional Case, IMS Meet- David, E. E., Jr., An Accurate of the Isomer Shift in Fe'. ing, Ithaca, N. Y. Estimate of the Glottal Wave - Wernick, J. H., see Bozorth, R. M. Brown, W. L., Semiconductor shape. Wernick, J. H., see Wertheim, Radiation Damage in Space, Mathews, M. V., see Lochbaum, G. K. Space Nuclear Conf., Gatlin - C. C. Wertheim, G. K., and Wernick, J. burg, Tenn. McSkimin, H. J., Bateman, T. B., H., Iron 57 Mossbauer Effect in Buchsbaum, S. J., Ion Plasma and Hudson, A. R., Some Meas- Cu -Ni Alloys. Waves, Massachusetts Institute urements of Wave Velocities Williams, H. J., see Geller, S. of Technology, Cambridge, Mass. and Elastic Moduli for Cad- Bugnolo, D. S., Information mium Sulphide. OTHER TALKS Theory and the Electromagnetic McSkimin, H. J., see Mason, Ahearn, A. J., . lass Spectro- Field, Cornell University Col- W. P. graphic Studies of Impurities in loquium, Ithaca, N. Y.

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www.americanradiohistory.com TALKS (CONTINUED)

Burton, J. A., Silicon p -n Junc- Commission Meeting, Yugo- of Am. New England Section, tion Crystal Counters, Bartol slavia. Boston, Mass. Research Foundation Seminar, Gnanadesikan, R., Probability Hittinger, W. C., Graduate Speaks Franklin Institute, Swathmore, Plots for the Gamma Distribu- for Industry, Business- Educa- Pa. tion, Institute of Mathematical tion Day, Bethlehem High Chisholm, D. A., Millimeter -Wave Statistics, Cornell University, School, Bethlehem, Pa. Traveling -Wave Tubes, Syra- Ithaca, N. Y. Hogg, D. C., Noise in Microwave cuse University, Syracuse, N. Y. Gresh, M., see Schwartz, N. Antennas, I.R.E. PGMTT, Clitherow, W. R., see Babington, Gupta, S. S., On Selecting a Sub- N. Y. C. W. set Containing the Population Holt, H. O., Programmed Self-In- David, E. E., Jr., Speaking with with the Smallest Variance, In- struction, The Park School, Computers, Second National stitute of Mathematical Statis- Buffalo, N. Y.; Summit Assoc. Symposium on Human Factors tics, Cornell University, Ithaca, of Scientists, Fairleigh- Dickin- in Electronics, Arlington, Va. N. Y. son University, Madison, N. J. Guttman, N., The Voice Mech- Holt, Books as Teaching David, E. E., Jr., Speech Analysis -A H. O., anism, and Recognition, I.R.E., Phila- Intercollegiate Musical Machines: Some Data, Midwest- delphia, Pa. Council, Columbia University, ern Psychological Assoc., Chi- N. Y. C. cago, Ill. Desmond, R. A., see Legg, W. E. Hansen, R. H., Problems in the Hostetler, W. E., The 5 -Type Drenick, R. Adaptive F., Systems, Preparation of Expanded Poly- Artificial Larynx, Service to I.R.E., PGCT, Philadelphia, Pa. propylene Insulation, Diamond Mankind (SERTOMA) Club, Egerton, L., see Jaeger, R. E. Alkali Co. Research Center North Indianapolis, Ind. Enloe, L. H., and Ruthroff, C. L., Seminar, Painesville, Ohio. Hunt, L. E., Performance Char- Threshold Effects of the FM Hansen, R. H., Hawkins, W. L., acteristics of a Horn -Reflector Demodulator with Feedback, Matreyek, W., and Winslow, F. Antenna, Seventh Regional U.R.S.I. /I.R.E. Joint Meeting, H., The Morphology of Semi - Conf. I.R.E., Phoenix, Ariz. Washington, D. C. crystalline Polymers. II: Oxida- Ingram, S. B., The Engineer in Fox, A. G., Resonant Modes in a tion of the Amorphous Region, Soviet Industry, Engineers Club Maser Inter erometer, Berkeley, Am. Chem. Soc. National Meet- of Vicksburg, Vicksburg, Miss. Calif. ing, Atlantic City, N. J. Iwerson, J. E., Recent Advances Fuller, C. S., Interactions of Im- Hanson, G. H., A Survey of Re- in Semiconductor Devices, Johns purities in Ge and Si, Universi- cent Progress in the Develop- Hopkins University, Baltimore, ty of Florida Chemical Depart- ment of High- Frequency Tran- Md. ment Seminar, Gainesville, Fla. sistors, Seventh Regional I.R.E. Jaccarino, V., Nuclear Magnetic Germer, L. H., Electron Diffrac- Conf., Seattle, Wash. Resonance in Superconducting tion Studies of Adsorbed Gases, Harmon, L. D., Computers and Intermetallic Compounds, Duke Cornell University, Ithaca, Brains, Watchung Regional University Physics Colloquium, N. Y.; Manhattan College, High School, Watchung, N. J. Durham, N. C. N. Y. C.; Esso Research Lab., Harmon, L. D., Artificial Neuron Jackson, W. H., see Spector, C. J. Linden, N. J. Studies, Michigan State Uni- Jacobs, I., Theoretical and Prac- Geusic, J. E., Physics of Masers, versity, E. Lansing, Mich.; tical Limitations of Weak -Sig- Ohio State University, Colum- Mental Health Research Insti- nal Processing Techniques, Sec- bus, Ohio. tute, Ann Arbor, Mich.; Uni- ond International Space Science Gianola, U. F., Magnetic Logic, versity of Michigan, Ann Arbor, Symposium, Florence, Italy. Electrical Engineering Depart- Mich. Jaeger, R. E., and Egerton, L., ment Seminar, Princeton Uni- Hawkins, W. L., see Hansen, R. Hot -Pressing of Alkali Niobates, versity, Princeton, N. J. H. Am. Ceramic Soc. Annual Gibbons, D. F., The Interaction of Hayes, J. S., Electron Beam Mi- Cony., Toronto, Ontario, Can- Acoustic Waves with the Con- croanalyzer: New Tool for ada. duction Electrons, Yale Uni- Electron Device Development, Jakes, W. C., Tracking Echo I at versity, New Haven, Conn.; Benjamin Franklin Hotel, Bell Telephone Laboratories University of Pennsylvania, Philadelphia, Pa. and Jet Propulsion Labora- Philadelphia, Pa. Herriott, D. R., Optical Properties tories, COSPAR Meeting, Flor- Gibson, W. M., and Miller, G. L., of the Cavity and Output Beam ence, Italy. Charge Collection in Semicon- of a Continuous Gas Maser, Javan, A., Optical Maser Oscilla- ductor Radiation Detectors, In- Quantum Electronics Conf., tions in a Gaseous Discharge, ternational Atomic Energy Berkeley, Calif.; Optical Soc. Columbia University, N. Y. C.;

266 Bell Laboratories Record

www.americanradiohistory.com Princeton University, Prince- gation, Ohio State University, Vacuum Microbalance Tech- ton, N. J.; Harvard University, Columbus, Ohio. niques, Washington, D. C. Cambridge, Mass. Pfahnl, A., Preparation and Prop- Stockbridge, C. D., see Warner, Jaycox, E. K., Participation in an erties of ZnO Phosphors, Elec- A. W. Optical EmissionClinic, Twelfth trochem. Soc., Indianapolis, Ind. Sumner, E. E., The 24- Channel Annual Symposium on Spec- Pierce, J. R., Satellites and Tele- PCM Exchange Carrier Sys - troscopy of Soc. for Appl. vision, International Television tem, Hillside School, Northern Spectroscopy, Chicago, Ill. Symposium, Montreux, Switz. New Jersey Institute of Radio Koonce, S. E., see Williams, J. C. Pierce, J. R., Some Practical Engineers, Montclair, N. J. Laudise, R. A., Hydrothermal Problems of Satellite Communi- Thurston, R. N., A Review of Crystallization, Union Carbide cation, The British Interplane- Some Russian Papers in Ultra- Research Center, Cleveland, O. tary Soc., London, England. sonics Engineering, I.R.E. In- Lawrence, W. A., Jr., Negative Pollak, H. O., A Mathematical ternational Cony., N. Y. C. Resistance of Anodically Passi- Theory of Defense, University Treves, D., Limitations of the fied Iron, Fairleigh Dickinson of Illinois, Urbana, Ill. Kerr Technique in the Observa- University, Rutherford, N. J. Pollak, H. O., On the Nature of tion of Magnetic Domains, Legg, W. E., and Desmond, R. A., Applied Mathematics, Univer- Minneapolis, Minn. Project Echo, Wall Township sity of Illinois, Urbana, Ill. Trumbore, F. A., Distribution Co- High School, Belmar, N. J. Reed, E. D., Solid State Maser, efficient of Antimony in Silicon Lowry, W. K., Machine Applica- Westchester Subsection of from. Solvent Evaporation Ex- tions to Library Functions, I.R.E., Westchester, N. Y. periments, Electrochem. Soc., American Cyanamid Co. An- Rosenthal, C. W., Automating the Indianapolis, Ind. nual Library Meeting, Metuch- Design of Digital Systems, Turner, D. R., Electrochemistry en, N. J. Seminar on Modern Topics in of Semiconductors and Its Ap- Mason, W. P., On Semiconductor Communications and Control, plications, Electrochem. Soc., Strain Gages, Soc. for Experi- Electrical Eng. Department, Detroit, Mich. mental Stress Analysis, Hud- New York University, N. Y. C. Warner, A. W., and Stockbridge, son- Mohawk Section, Rensselaer Rowen, J. H., Solid State Devices, C. D., Mass and Thermal Meas- Polytechnic Institute, Troy, Soc. for Industrial and Applied urement with Resonating Cry - N. Y. Mathematics, Monterey, Calif. stalline Quartz, Second Infor- Matreyek, W., see Hansen, R. H. Ruthroff, C. L., see Enloe, L. H. mal Conf. on Vacuum Microbal- McLean, D. A., Tantalum Film Schawlow, A. L., Fine Line Capacitors and Resistors, Spec- ance Techniques, National Bu- tra of Chromium Ions in. Alumi- reau of Standards, Wash., D. C. A.I.E.E. /I.R.E., Ogalalla, Neb. num and Magnesium Oxide, Wertheim, G. K., Some Applica- McNamara, M. L., Anomalous Physics Department, Stanford tions of the Mossbauer Effect Breakdown Characteristics in University, Palo Alto, Calif. in Magnetism, Silicon Diffused Junctions, Elec- Naval Research Schawlow, A. L., Optical Masers, Lab., Washington, D. trochem. Soc., Indianapolis, C. I.R.E. Prof. Gp. on Ind. Electron Williams, J. C., Sinclair, W. R., Devices, N. Y. C.; Stanford Meitzler, A. H., Transmission and Koonce, S. E., Preparation University, Physics Colloquium, of Thin Alurnino- Silicate Filins, Characteristics of Longitudinal - Palo Alto, Calif. Mode, Strip Delay Lines Hav- Am. Ceramic Soc., Toronto, ing Asymmetrically Tapered Schwartz, N., and Gresh, M. Canada. Polarity of Tantalum Widths, 1961 I.R.E. Interna- Oxide Williams, W. H., Generating Un- Printed Capacitors, Electro- tional Cony., N. Y. C. biased Ratio and Regression chem. Soc., Miller, E. E., see Babington, W. Indianapolis, Ind. Estimators, Columbia Univer- Miller, G. L., see Gibson, W. M. Scovil, H. E. D., Solid State sity, N. Y. C. Montgomery, H. G., Fluctuation Masers as Low Noise Amplifiers, Winslow, F. H., see Hansen, R. H. Phenomena in Solids, Fifth I.R.E., PGMTT, Wash., D. C. Wintringham, W. T., The Prin- Fluctuation in Solids Symposi- Sinclair, W. R., see Williams, J. C. ciples of Color Television, um, Armour Research Founda- Sliehter, W. P., The Study of Thirtieth Annual Meeting of tion, Chicago, Ill. Glass Transitions by Nuclear Inter -Soc. Color Council, Ro- Moore, E. F., Machine Models of Magnetic Resonance, Polytech- chester, N. Y. Self-Reproduction, Mathemati- nic Institute of Brooklyn, N. Y. Yokelson, B. J., Electronic Switch - cal Problems in the Biological Spector, C. J., and Jackson, W. H., ing System, A.I.E.E., N. Y. C. Sciences Symposium, N. Y. C. Tantalum Film Circuits, Elec- Zacharias, A., A Precise Method Mumford, W. W., Some Technical tronics Components Conf., San for Measuring the Incremental Aspects of Microwave Radia- Francisco, Calif. Phase and Gain Variations of a tion Hazards, I.R.E. Prof. Gp. Stockbridge, C. D., A Vacuum Traveling -Wave Tube, 1961 on Microwave Theory and Tech- System for Mass and Thermal I.R.E. International Meeting, nique and Antenna and Propa- Measurement, Second Conf. on N. Y. C.

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www.americanradiohistory.com THE AUTHORS

and signaling systems and station in signaling and radio telephony switching systems. Mr. Michael and has written numerous tech- is a graduate of New York Uni- nical articles. He is a Senior versity with degrees of B.A. in Member of the Institute of Radio mathematics and M.S. in physics. Engineers. He is co- author of the article "SAC'S Primary Alerting Sys- tem" in this issue of the RECORD.

Harold M. Pruden, co- author of "sac's Primary Alerting Sys- tem," joined the Western Electric Company's Engineering Depart- ment in 1919. This group was later incorporated as Bell Labora- H. J. Michael tories. He has specialized in the development of signaling systems for long distance telephone cir- a of Long H. J. Michael, native cuits, and for transoceanic, ship - Island, joined the Laboratories in to -shore and mobile radiotele- 1929. He has engaged in studies phone systems. He also contrib- relating to transmission quality, uted to the development of remote including the physical characteristics of speech and the structure Oscar .Myers, co- of the of telephone conversation, signal- author Dialing, was ing and switching development, article on Overseas and during the war, the design of born in Hartford, Connecticut. underwater weapons. Since the Inmiediately after receiving the Bachelor of Chemistry war, Mr. Michael has engaged in degree of in 1921 the design and development of the from Cornell University he joined Western Electric. In No. 5 crossbar system. He joined the Engi- the American Telephone and Tele- 1924 he transferred to neering Department of the Coin - graph Company in 1952, and after pany which became Bell Labora- two years in its Administration B tories. Mr. Myers helped design Department, he rejoined the Lab- and develop No. 1 Crossbar, No. 5 oratories in the Special Systems Toll Systems, Engineering Department. He now Crossbar, Crossbar and Crossbar tandem. He holds heads a group concerned with 39 patents received in connection studies of private line switching O. Myers with this work. He was a member of the Bell System team which planned and negotiated ar- control devices for unattended re- rangements for dialing to Europe peater stations along coaxial over ocean cables. He also worked cable and microwave telephone on the planning of the Hawaiian transmission routes. During World and Alaskan cables. At present War II, Mr. Pruden was engaged Mr. Myers is Switching Systems in work on radar and short -wave Engineer in charge of a number radio transmission for the armed of projects among them the plan- forces. He later returned to work ning of switching and numbering on mobile radio- telephone sys- for world -wide dialing. He is one tems and remote control systems of the Bell System representa- and also took part in work on the tives to the CCITT. Nike missile project. He is cur- Carl A. Dahlbom, a native of rently on field assignment in Cali- Brooklyn, New York, has been a fornia. Mr. Pruden has been member of the Laboratories since H. M. Pruden granted 17 patents for his work 1930. His first assignment was in

268 Bell Laboratories Record

www.americanradiohistory.com AUTHORS CONTINUED!

the Telegraph Department where years. Since his return to the ated from the University of Min- he worked on transmission and Laboratories in 1952, Mr. Jack- nesota with the degree of B.S. in circuit development. During son has been engaged in the de- E.E., in 1923, and an M.S. in World War II he was engaged in sign of equipment for supplying 1925, following a year of service the development of military tele- dry air to waveguides and anten- with the Northwestern Bell Tele- graph and speech secrecy sys- nas of radio -relay networks and phone Co. in Minneapolis. He tems. Following that he was as- to cable systems. While working joined Bell Laboratories immedi- signed to work in design of single at the Laboratories, Mr. Jackson ately thereafter. and multifrequency signaling sys- attended Rutgers University and Throughout his telephone ca- tems. At present Mr. Dahlbom was made a Member of Technical reer, Mr. Kannenberg specialized is Signaling Systems Engineer Staff in 1957. in development of equipment as- and is responsible for formula- sociated with carrier systems and tion of signaling systems require- he took part in work on the first ments for toll, exchange and submarine telephone cable be- subscriber line facilities. Mr. tween Cuba and the U.S. He was Dahlbom received the degree of "loaned" to the Western Electric -1 B.E.E. from Brooklyn Polytech- Co. in 1942 to aid in setting up a nic Institute in 1941. He is a new factory to manufacture parts senior member of I.R.E. He is co- for carrier systems. author of the article on Overseas During most of World War II Dialing in this issue. Mr. Kannenberg was engaged in work on microwaves and radar for J. M. Jackson, the author of military applications. In 1946 he "Air- Drying Apparatus for Mi- turned to work on acoustic prob- crowave Systems" is a native of lems and took part in develop- Fanwood, N. J. Shortly after ment of systems related to res- joining the Outside Plant Devel- taurant W. M. Fox music installations. From opment Department of Bell Lab- 1950 to his retirement in Septem- oratories in 1942, he entered the ber, 1960, he engaged in studies Navy where he served until 1945. W. M. Fox, the author of "A of magnetic problems for military Self- Protecting Transistor for and civilian applications. The E -6 Repeater" in this issue, Mr. Kannenberg holds more is a native of Bethlehem, Penn- than 30 patents relating to many sylvania. He received undergradu- phases of his work. He is a mem- ate and graduate degrees in ber of the American Institute of Physics, the B.S. from Muhlen- Electrical Engineers, the Acous- berg College in 1951 and the M.S. tical Society of America, from St. Lawrence and University in Sigma Xi. 1953. From 1953 to 1957 Mr. Fox was associated with the Research and Development Laboratories of the Franklin Institute where he did basic research in solid -state physics. In 1957 he joined Bell Laboratories and was assigned to the Allentown Laboratory where he has been working on the final J. M. Jackson development of transistors. Mr. Fox is a member of the Research In 1945 he returned to the Lab- Society of America and of Sigma oratories and was associated with Phi Sigma. projects on joining and maintenance methods for telephone Walter F. Kannenberg, author cables. of "Static Frequency Generators During the Korean war he was for Ringing Power," was born recalled to Naval service for two in St. Paul, Minnesota. He gradu- W. F. Kannenberg

www.americanradiohistory.com PIONEERING AT BELL TELEPHONE LABORATORIES

In such an open field as this Dr. Karl Jansky of Bell Laboratories opened the way to radio astronomy. His search for a mysterious source of radio noise led him -and us -to the stars for our answer. Today Bell scientists continue their pioneering in many fields -among them the transmission of human voices on beams of coherent light. Bell Laboratories' revolutionary Optical Maser foreshadows the use of light as a whole new medium of telephone, TV and data communications. These are but two of the many fundamental advances which have come from breaking fresh ground at the world center of communications research and development.