Eletoz/Vie Patented Sept
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Sept. 7, 1926. 1,598,673 O. B. BLACKWELL ET AL SECRECY COMMUNICATION SYSTEM Filed Dec. 18, 1920 R (2AA%aeaeAA 8 eletoz/vie Patented Sept. 7, 1926. 1,598,673 UNITED STATES PATENT office. OTTO B. BLACKWELL, OF GARDEN CITY, NEW YORK; DE Loss K. MARTIN, or oRANGE, NEW JERSEY; AND GILBERT S. VERNAM, OF BROOKLYN, NEw YoRK, AssGNORs TO AMERICAN TELEPHONE AND TELEGRAPH. COMPANY, A CoRFoRATION of NEW YORK, sECREGY coMMUNICATIoN sYSTEM. Application filed December 18, 1920. Serial No. 431,721. This invention relates to a signaling sys pear more fully from the detailed descrip 50 tem wherein signals are transmitted by the tion hereinafter given. agency of a high frequency wave modu The arrangements of the invention are ill lated in accordance with said signals, and lustrated in the accompanying drawing, in more particularly to a signalling system em the figure of which is shown a sendingsta ploying a plurality of high frequency tion of a system embodying the invention. 35 waves. It is the object of the invention to In the arrangements of the drawing are rovide a system of communication where shown four low frequency channels 1, 2, 3 y secret communications between stations and 4 from which the low frequency sig 10 may be had to the end that stations, other nals, such as four telephone messages, may than those designed to receive, may not re be transmitted through modulating appara 60 ceive complete, intelligible signals. tus out over a transmission line L. The Heretofore in certain types of signaling modulating apparatus is shown schemati systems, in which a high frequency wave is cally and includes the modulators M., M., 15 utilized as the agency for transmitting the Me and Ma, with which are associated the signals, he signals have been transmitted high frequency sources A, B, C, and D, 65 by electromagnetic waves of a definite high which are of suitable different frequencies. frequency or wave length and any station These modulators may be of the duplex vac tuned to said wave length might be capable uum bulb type illustrated in the U. S. 20 of receiving said signals. In the present. Patent #1343,307, dated June 15, 1920, in invention secrecy is obtained by the trans the name of John R. Carson, although other 70 mission of signals on a plurality of waves types of modulators may be used. These of different frequencies, successive portions modulating devices are associated with the of a message being transmitted on waves of low frequency channels 1, 2, 3, and 4, by 25 different frequencies whereby a station means of the hybrid coils 17, 18, 19 and 20, tuned to one of said waves receives only a the conductors 5, 6, 7 and 8, and over the 5 partial and therefore unintelligible disclo contacts of a plurality of series of relays, sure of the communication. The arrange such as the relays 13, 14, 15 and 16, and the ments of this invention present the addi relays 9, 10, 11 and 12. Associated with 30 tional secrecy feature that the shifting of the above mentioned hybrid coils are the the low frequency signals or portions of the balancing networks N, N N and N. In 80 message, to the various high frequency cluded in output circuits of the modulators waves or channels is not accomplished in a are the band filters F, F, F, and F, which cyclic order but rather in a random and va readily transmit the band of high frequen . 35 riable manner. To this effect printing tele cies of the order of the particular high fre graph apparatus and key tapes are utilized quency source associated with each modula 85 to shift the low frequency signals in a va tor but which attenuate and practically ex riable manner to the high frequency chan tinguish frequencies outside of said band. nels, the shifting being controlled in ac These filters may be of the type illustrated 40 cordance with the perforations and setting in the U. S. Patents No. 1227,113 and No. of the key tape utilized. With this ar 1,227,114 to G. A. Campbell. The output O rangement the messages would be unintel circuits of the modulators are associated ligible to unauthorized persons, who might with the line L through the hybrid coil 21, . have access to the medium through or Over the conductors 22 and the high pass filter 45 which the messages are transmitted, unless F. The filter F, readily allows the trans such persons should be provided with the mission of the high frequency carrier cur 95 key tapes utilized at the sending station in rents utilized but attenuates and extin addition to other information. * Other ob guishes the low frequency currents trans jects and features of the invention will ap mitted over the line L, such as of the nor 1598,078 mal speechor telegraphic frequencies. In order that the messages coming in over line transmitter to be pulled down and will step I may be received over the lines 1,2,3 and brushthe {{???? passes of keyof segment tape ahead. 32 the magnetWhen the 35 4, there is associated with the high fre will be released and the contacts of the trans quency sources A, B, C and D, the demodu mitter will be pressed against the key tape. () lating devices IDM, DM, DM, and DM, If there are no holes in the perforated key which may be of the duplex vacuum bulb tape, the contacts 39 and 40 will remain open type illustrated in the U. S. Patent No. as shown Under such conditions none of 1343,308, dated June 15, 1920, to J. R. Car the relays 9, 10, 11 and 12, or the relays 18, . 10 son. Included in the input circuits of the 14, 15 and 16, will be operated. Under these 5 demodulators are the band filters F. F. F. conditions, line 1 will be connected to the and F, adapted to readily transmit bands modulator MA over the back contacts of of frequencies respectively such as those relays 9 and 18, over conductors 5, and from the sources D, C, B and A and to at through hybrid coil 17. The line 2 will be ls tenuate and extinguish frequencies outside connected to the modulator Ma over the 80 of said bands. The output circuits of the back contacts of relays 10 and 14, conductors demodulators are associated with the lines 6 and the hybrid coil 18. Line 3 will be con 1, 2, 3 and 4, by means of the hybrid wind nected to the modulator Mc over the back ings 17, 18, 19 and 20, conductors 5, 6, 7 and contacts of relays 11 and 15, conductors 7 20 8, and over the contacts of the series of re and the hybrid coil 19. Iine 4 will be con 86 lays, such as relays, 13, 14,15 and 16, and nected to the modulator M over the back relnys 9, 10, 11, and 12. The operation of contacts of relays 12 and 16, conductors 8 the series of relays, such as relays 9, 10, 11 and the hybrid coil 20. It is pointed out that and 12, and relays 13, 14, 15 and 16, is con under such conditions the low frequency sig 25 trolled by the printing telegraph transmit ter 36, the contacts 39 and 40 of which are nals from the lines 1, 2, 3, and 4 will be im controlled by a perforated key tape, not ressed on different high frequency waves shown. Associated with the tape transmit thenfrom bethe transmitted sources A, outB, overC, and the D,line and L inwill a ter is the distributor 29 for timing the se well known manner. When the brush of the 30 uence of operation of the arrangements. distributor crosses segment 33, a circuit will le distributor 29 is associated with a re be closed over conductor 37 and through the lay, 26 and the pole changing apparatus 25, winding of relay 88, to battery, and ground, which in turn is associated with the usual thereby energizing relay 38. However this type of composite set 23 associated with the will have no effect at this time as neither of line L. Associated with composite set 23 is the low pass filter F, which readily allows the contacts 39 and 40 were operated and the transmission of the low frequency cur 14,none 15, of andthe relays16 were 9, 10,previously 11, and 12operated. and 13, rents, such as the telegraph currents and the When the brush of the distributo again currents from the pole changing apparatus 40 crosses segment 31, the relay 26 and the pole 25, but which shuts out the high frequency changing device 25 will operate as previously 105 carrier currents. pointed out to transmit an impulse to the dis Operation of the sending arrangements of tributor at the receiving station. When the the invention is as follows: brush now crosses segment 32, the magnet 35 The perforated key tape will be inserted will again be operated and will pull down in the tape transmitter 36 and the key K the contacts and will step the key tape ahead. O thrown. The throwing of key K will close a For purposes of illustration let us assume circuit for the relay 30. This will release that the perforations in the tape are now so the latch and allow the brush of the distrib arranged that contact 39 may be closed and 50 utor to start rotating.