Patent GB-876983-A (GB)
Title: Translator for a telephone system
IPC: H04Q3/42
Filed: 1957-07-10
Abstract: 876,983. Automatic exchange systems. GENERAL TELEPHONE LABORATORIES Inc. July 10, 1957 [Aug. 1, 1956], No. 21927/57. Class 40 (4). A translator includes a plurality of rectifierresistance aggregates each connected on its input side to a predetermined combination of incoming marking conductors and connected on its output side to another predetermined combination of outgoing marking conductors, thereby to translate a combination of registered digits into a combination of translated digits, the incoming marking conductors being marked by connecting thereto the potential corresponding to one terminal of the exchange battery and each rectifier-resistance aggregate comprising a switching transistor having one of its electrodes connected to the incoming marking conductors, another electrode connected to the outgoing marking conductors, and its third electrode connected to the aforementioned terminal of the exchange battery, so that the transistor upon changing its state of conductivity acts to connect to the outgoing marking conductors the potential corresponding to the aforementioned terminal of the exchange battery. As shown, after the initiation of a call from a sub-station T1, a register 70 applies a marking potential of either earth or - 48 volts to each conductor of three groups 100, 105, and 110, each containing four conductors, in a binary code according to the first three (exchange code) dialled digits. The translator contains a plurality of units 80A, 80B, &c., one unit for each exchange to which a calling sub-station has direct dialling access. Taking translator unit 80A as an example, it comprises a transistor TR120 connected in a grounded-collector circuit. The base of the transistor is connected through a plurality of diodes such as D130 to those conductors of the groups 100, 105 and 110 which are marked with earth potential when the associated exchange code digits are dialled and registered. The emitter is connected through one or more diodes such as D150 to a selection of conductors in three groups 200, 205 and 210 according to a binary code to give the corresponding routing digits. Normally the base is maintained at a potential of approximately -40 volts, and so are the emitter and the conductors connected to it. When the office code digits (" 137 " as shown) associated with the translator unit 80A are dialled and registered, the earth markings applied to the relevant conductors in groups 100, 105 and 110 cause all the diodes such as D130 of the unit 80A to be biased non-conductive so that the base and hence the emitter of transistor TR120 are established at substantially earth potential. Thereby the diodes such as D150 and those conductors of the groups 200, 205 and 210 which are connected thereto are established at earth potential, marking the required routing digits (" 231 " as shown) to the sender 90. Every other translator unit such as 80B is unaffected, since at least one of its diodes such as D170 remains conductive. If the calling subscriber dials the exchange code digits "481," translator unit 80B marks the routing digits " 763 " to the sender 90, and so on.