The Early Years of the Strowger System

.panies are re stomers regfird,- feature, some The Early Years hods of piovid, ns and the spe areas post cards ,hen the service of the LOges occur. In .s are ,adequate. ate what,opel'a 'ormation. Strowger System nst "listen to all itY of the eight 'ach subscriber ,e teti:party sys riber hears £lve, R. B. HILL Almon B. Strowger in his later 'ide a 'ten-party General Staff years, fram "Telephony" tor Oc ,bscriber would tober 15. 1949. require an addi lis was found to Some of the early attempts to devise anto the central office for each subscriber line. matic telephone systems were described The switch consisted essentially of a hollow briefly inc a previons article", and it was cylinder with a shaft capable of both verti stated that, while some of the early inven cal and rotary motjon. This shaft carried a hips tions embodied ideas that were later devel- ' wiper arm capable of wiping over all the tre designed to oped into important featores9f the modern horizontal rows of contacts on the inside of ch in the funda automatic art, none of the systems them the cylinder. All of the subscriber lines were selves went into commercial use. Itremained multipled to the rows of terminals around Since they were for Almon B. Strowger, an undertak~r of the cylinder of every switch, while one of {Ships nave been Kansas City, Mo., to devise the first auto the subscriber lines was connected to the tnt $4,000 to the matic telephone system to be used commer wiper of each switch. Strowger did not spe .hip and $1,500 cially. The important featore of this inven cify in his patent the maximum number of tion was that of imparting to the switch m;m lilies which could 'be terminated in his "ducted"" creative £lrst a vertical movement, and then' a rotary switch. but in a circular issued in April, lading centers of motion in a horizontal plane. Strowger is said 1891, he claimed that itwould "connect tele "pient being free to have constructed the first crude model of phones in aIsystem from two to ten thou it which he will his switch from a cardhoard collar box and a sand." In describing its method of operation, Jps are awarded paper of pins. He stock the pins from the however, most writers have assumed ten )ommittee of sci outside of the box toward the center until horizontal rows of 100 contacts each. (Even staff of Bell Lab he had ten horizontal rows of ten pins each, this number would have required a switch are the research one row above the other, to represent tbe prohibitive in size and cost.) The vertical 1e importance of line terminals. The vertical shaft for carry and rotary motions of the shaft were con d the likelihood ing the switch arm was represented by a trolled by electromagnets actoated by im ist. The ,awards lead pencil through the center of the box. pulses sent from the subscriber station. Four have recently re Strowger filed his patent application on push buttons on the subscriber telephone l' who are about March 12, 1889, and it was issued on March box each controlled a wire to the central 10, 1891 as patent No. 447,918. The mecha office, while the fifth wire was for talking. nism of Strowger's patent is shown in Fig To call the number Bl5, Strowger states ure 1. While this particular arrangement in his patent, the subscriber pressed his was never used commercially, it illustrates "hundreds" button (d) three times, thus the inventor's original ideas. As may be lifting the shaft of his switch three notches seen, an individual switch was required at and bringing the wiper opposite the third , RECORD, January, 1955, page 22. row of terminals. He then pressed his "tens" loratories Record March, 1953 95 Courtesy www.historyofphonephreaking.org button (H') once, which gave a single rota button after a conversation was finished. tion to a 10-toothed ratchet wheel (E') at In 1893, a small Strowger equipment was tached to the shaft and moved the wiper exhibited at the Chicago World's Fair. arm to 310. Pressing the "units" button (I') About the beginning of the year 1894, !lve times operated a 100-toothed ratchet Frank A. Lundquist and the Erickson broth wheel (E) attached to the shaft and moved ers, John and Charles J., entered the service the wiper arm five more points to 315. of the Strowger company, and, with A. E. Ringing was done with a magneto or bat Keith, started work on an improved system tery. When through talking, the calling sub employing the so-called "piano wire" ter scriber pressed the (p') button, which ener minal banks with a Hat-faced multiple and gized the release magnets and brought the a Switch arm capable of both a rotary and a shaft and wiper arm back to their normal longitudinal movement. Switches of this positions. The use of five wires and ground .type, which were covered by patent No. was, of course, an impractical feature, but 540,168, were installed at La Porte, Ind., in Strowger planned to later reduce the num the fall of 1894 to replace the original equip ber of wires. A heavy battery was to be em ment, and at Michigan City, Ind., inthe same ployed at each sub-station for operating the year. These new installations employed a central office switch. There was nO provision simple form of busy signal. When the call against the calling subscriber being con ing subscriber rang, both bells responded nected to a busy liue. if the called line was free. If it was busy, The first company was incorporated on the calling subscriber bell remained silent. October 30, 1891, under the name of the They also utilized the !lrst automatic re Strowger Automatic Telephone Exchange. lease arrangement, invented by A. E. Keith Early in 1892, A. E. Keith, who had pre in 1893 and covered by patent No. 573,884, viously been employed by'the Brush Elec embodying a mercury switch connected with tric Company, of Baltimore, entered the the subscriber switehhook, which restored service of the Strowger company and was the central office switch to its normal posi for many years thereafter one of its leading tion upon the hanging up of the receiver. technicians and inventors. The "piano wire" form of switch did not On November 3, 1892, the first Strowger prove successful, and in 1895 a return was exchange was opened for public service at made to the principle of Strowger's original La Porte, Ind., with about seventy-five sub patent. Patent No. 638,249, issued to A. E. scribers. This was the first automatic tele Keith and the Erickson brothers, covered a phone exchange to be installed anywhere, switch which more nearly resembled the and a considerable amount of ceremony was modem step-by-step switch. Twowews of attached to the affair, with a special train it in the patent are shown in Figure 2. It run from Chicago and a brass band on hand employedsemi-circular banks and the famil to greet the guests. Since this system was iar "up-and-around" motion of the selector designed for less than 100 lines, there was rod and wipers. One-hundred-line switches no need for a switch with a two-way move of this type replaced the "piano wire" ment, and a flat rubber disc type of switch switches at La Porte in June, 1895. In Aug was employed, with but one (rotary) move ust, 1895,' a similar system, with 200-line ment for the wiper arm and one circular row ,"witches, was installed at Michigan City. of contacts. There were still five line wires, At this time, the Strowger system em as in Strowger's patent, aud each telephoue. ,ployed., betw'een a subscriber's premises and was equipped with four push buttons, al the central office, two hard drawn copper though the hundreds button was not used. line wires, and a soft copper battery wire The battery for operating the switches was which branched into all the stations to sup now located at the central office. There was ply signaling current. This arrangement con still no provision against a subscriber being tinued in use until about the year 1900. connected .to a busy line. The system In the summer of 1896, an important for worked with reasonable accuracy wh'Jn the ward step was made with the introduction subscribers operated their push buttons cor of the fuiger-wheel dial to replace the push rectly and remembered to press the release buttons. It was covered by patent No. 597,- Fig. l-:Strowger', 96 Bell Laboratories Record ( March, 1953 Courtesy www.historyofphonephreaking.org was finished. :quipment was_ old's Fair. he year 1894, :rickson broth red the service ld, with A. E. proved system lilO wire" ter 1 multiple and a rotary and a itches of this by patent No. Porte, Ind.,ift original equip" ld.) in the sam~ IS employed a When the calI ells responded [f it was busy, ~mained silent. automatic re by A. E. Keith at No. 573,884, connected with which restored ts normal posi the receiver. switch did not 5 a retnrn was Iwger's original issued to A. E. hers~ covered, a resembled the Two views of in Fignre' 2. It s and the famil of the selector ·d-line switches cCpiano w:fre~~ " 1895. In Aug , with 200-line Hchigan City. ;er system ern IS premises and drawn· copper or battery wire stations to sup rangement con le year 1900.

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