Patent GB-617932-A (GB)
Title: Improvements in telephone switching systems
IPC: H04Q3/42
Filed: 1946-08-01
Abstract: 617,932. Automatic exchange systems. WESTERN ELECTRIC CO., Inc. Aug. 1, 1946, No. 23000. Convention date, Aug. 14, 1945. [Class 40 (iv)] In a toll switching system in which connections between a toll office and other local or toll offices are made under the control of a register-sender, when the register-sender has registered a predetermined number of digits sufficient to enable at least a part of the routing to be determined, it is at once connected to a pretranslator which identifies the class of call by means of those digits and is thereupon released, after causing the register-sender to be associated with the appropriate one of a plurality of markers, which then effects the required toll or local office connection. A system comprising two toll offices P, Q is shown schematically in Fig. 1. At P an operator's position 12 includes jacks 10, 13, a cord 11 and an outgoing trunk circuit 14 connected by trunk 15 to the incoming trunk circuit 16 at office Q which has access to the registersender 17. This is connected by the markerconnector 18 to the pretranslator 19 and may under the control of the pretranslator be selectively connected to toll completing marker 20 or inter-toll marker 30. The inter-toll marker 30 includes area translators 31, 32 individual to the marker 30 and translator 33 common to all inter-toll markers in office Q. Toll completing and inter-toll trains of switches 40 and 41 respectively are associated with outgoing trunk circuits 50 and 51, leading to local and toll offices respectively. Detailed description (Figs. 2-6). The first figure of a three-figure reference numeral corresponds to the number of the Figure in which it is to be found. Incoming digits over the trunk 15 are received by the pulse-receiving circuit 200 of the register-sender and are registered successively in the relay registers 211 ... 220 under control of the sequence relays 201 ... 210. As soon as the third digit is registered, ground is connected to conductor 223 and brings up relay 400 which releases 401 (previously operated when the register-sender was seized). Relay 402 then pulls up followed by 409 and 410 in an idle marker-connector. This last relay is followed by 360 and a translator preference relay 425 associated with an idle pretranslator 19 (Fig. 5). Subsequent operation of 430 connects the register-sender to the pretranslator. Each of the contacts 411 ... 413 of relay 410 and 431 ... 433 of 430 represents a set of four contacts over which the registers of the sender and pretranslator are connected. Seven route relays 503 to 509 are provided, one of which is operated over contacts of the register relays in accordance with the route code registered, e.g. 503 operates to the code 243 as shown. These route relays serve to provide information as to the class of call. Code terminals, one per route relay, are provided and are cross-connected to class terminals, one per class of call. The code terminals of route relays corresponding to local offices to which calls are routed directly are cross-connected to class terminal 535; those for local offices reached through the same toll office, to which there is a direct group of trunks, to 536; those for a toll area to which there are several direct trunk groups each terminating in a different toll office, to 537 ; those for a toll area to which there is a single direct group of trunks, to 538; and those for a toll area reached via an intermediate toll office, to 539. Call to local office reached directly. If the first three digits registered are 243, relays 501, 502 operate and bring up route relay 503, so that ground is extended through class terminal 535 to energize class relay 450 in the registersender, followed by 499, 455 and 340. Relay 499 disconnects 425 which releases 430, thus disconnecting the register-sender from the pretranslator, and operates marker preference relay 369. The last relay brings up 380 which extends the leads from the A, B and C registers of the register-sender to those of the toll completing marker 20 (Fig. 6). This marker then controls the selection of a trunk leading directly to the called local office and the completion of the connection through the switch train 40. The register-sender transmits over the outgoing trunk the numerical digits of the called party's number by means of the outgoing pulsing circuit 300 under the control of the sequence relays 311-320 and 321-330, beginning with relays 314 and 324. Call to local office reached through another toll office over a direct trunk. Assume that the code transferred to the registers of the pretranslator operates route relay 506. Ground extended through class terminal 536 brings up class relay 460, followed by 499, 465 and 340. The pretranslator is disconnected as before and operation of marker preference relay 365 and relay 370 associates an intertoll marker 30 (Fig. 6) with the register-sender. With both relays 600, 610 normal, the common translator 33 is used to operate a route relay and thus select an outgoing trunk in a group leading directly to the terminating toll office. The connection is established over the switch train 41. The register-sender transmits both the local office code and the called party's number since the sequence relays 311, 321 are the first to be operated in this case. Call to toll area to which there are several direct trunk groups each of which terminates in a different toll office. The first three digits bring up route relay 507 and ground extended over class terminal 537 brings up class relay 470 followed by 499 and 350. The pretranslator is disconnected but no marker is connected up until an additional three digits (the local office code) have been registered in the register-sender, whereupon relay 465 pulls up and is followed by 365, 370 and 610. The D, E and F registers of the register-sender are thus connected to the A, B and C registers respectively of the intertoll marker 30, and thence to the area translator 31. If the class relay operated indicates that the area translator 32 is to be used, relay 600 is operated (over a circuit not shown) in place of 610. A route relay is next operated and controls the setting up of the connection over the switch train 41 to an outgoing trunk in a group leading to a toll office from which the called local office is directly accessible. The local office code and the called party's number are transmitted over the trunk under the control of the sequence relays beginning with 314 and 324. Call to toll area to which there is a single direct group of trunks. Route relay 508 is operated by the first three digits and class relay 480 is energized, followed by 499, 465 and 340. The registers of the intertoll marker 30 are associated with the A, B and C registers of the register-sender as previously described and with the common translator 33, whereby a route relay is operated to effect the selection of a trunk in a group leading directly to the called toll office. If the trunk is a ring-down trunk no transmission of digits takes place, but if the trunk is a dial trunk, the local office code and the called party's number are transmitted, relays 314, 324 being the first of the sequence relays to operate. Call to toll area not directly accessible. Route relay 509 operates and brings up 540, followed by 480, 490, 499, 465 and 340. The A, B and C registers of the register-sender are thus connected to the registers of an intertoll marker 30 and thence to the common translator 33 as above. The operation of the route relay corresponding to the toll code digits effects the selection of a trunk in a group leading to another toll office from which the called toll office is directly accessible. The class relay 490 therefore disconnects ground from lead 491 to prevent immediate operation of 314, 324 and connects ground to 492 so that 311, 321 come up first. The toll code digits are thus transmitted over the trunk in addition to the local code digits and the called party's number, since they are required at the tandem toll office to control the further routing of the call.