Patent GB-517993-A (GB)
Title: Improvements in or relating to identification of subscribers in telecommunication exchange systems
IPC: H04M15/08
Filed: 1938-08-13
Abstract: 517,993. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. (Hatton, W., Kozma, L.). Aug. 13, 1938, No. 23923. [Class 40 (iv)] In an inter-exchange system in which the identity of a sub-station at one exchange is signalled to and recorded at a second exchange, an identification signalling connection is set up from the second exchange to the first over an idle one of a group of conversational junctions between the exchanges. Identification is given priority in a busy group of junctions. In the system shown in Fig. 1, a con versation connection from exchange A to toll exchange T is set up over IGS, ENGS at B, to TIGS at T where recording of the calling number at ticketing equipment P under the control of circuit TC is required. A connection may also be initiated at tandem and set up over IGS, TIGS. When TC is ready to receive the identity of the calling party, it signals a connecting circuit IL at toll whereupon CF hunts for the conversation circuit and JF selects, over OJC, a junction back to B in a group determined by the setting of CF. Circuit IL thereupon sends a digit to incoming group selector WNGS at tandem to direct it to a group of identification selector circuits IT to which it has access in addition to normal conversation trunks. After an idle circuit IT has been seized, a switch TF therein is set by two digits, determined by IL at toll, so that it makes connection with the conversation circuit of which the calling line requires identification. If the connection originated at tandem, circuit IT sends a start signal over the 4th . wire to identifying equipment IC at tandem which identifies the line and sends the number over the 4th wire to IT which repeats it over the identification junction and IL at toll to TC. If the connection originated at exchange A, IT at tandem sends a different start signal to IL at tandem which thereupon sets up an identification connection over 'OJC and a junction to A where circuit IT calls for and receives the identity from IC. Circuit IL at tandem repeats the identity over the exchange trunks to IT which repeats it to IL at toll as before. Setting up the identification connection.-' When the control circuit TC is ready to receive. the number of the calling party, it grounds wiper d, Fig. 2, of the incoming selector TIGS at toll to operate Mt whereupon relays Fs,. Ss, common to the junction group, and start relay St, common to a number of groups, pull up to start finders OF of idle circuits IL over home contacts of switch D. When one of them finds the conversational circuit, Ct operates followed by Ch for double testing and relays Fs, Ss, St relapse. Relay Cb pulls up to start JF searching for a junction back to tandem in the same group as the conversational junction, St being operated over group multiples of CF and JF and battery on lead 6 of an idle outgoing junction circuit, Fig. 4. Jh completes the double test and operates Jb which causes switch D to take a step and connects relays Aw, Bw to the a and b wires of the junction circuit to seize the incoming selector at tandem. Aw and Bw connect interrupter D1 to impulse relay Is which pulls up on the first pulse followed by Bd and sluggish relay Id. On relapse of Is, Nm pulls up over a circuit which locks Bd and connects battery and ground to the junction in a circuit controlled by Is, relays Aw, Bw being released. Further impulses are repeated over the junction and to magnet CM of switch C, bank c of which is connected to junction group marking wires in bank e of JF and banks e and f of CF, but as switch D is in position 2 only the marking over JF is effective, and when C reaches the marking Ed pulls up to disconnect the interrupter and is held by slow release relay Id. In response to the 'impulse train, incoming group selector WNGS at tandem has been directed to the correct group of circuits IT and hunts for an idle one. Relay Ed releases Nm and Bd followed by Id slowly, whereupon CM intereacts with X to home switch C, and D takes a further step to contacts 3 when Ed relapses. When the group selector seizes IT, Figs. 5 and 6, Cw operates over the test-wire and S pulls up in series with Aw, Bw which have been re-connected at IL, and is followed by Cl and Ic and the completion of the heating circuit of valve DV. Impulses are again transmitted as before from IL at toll but the train is now terminated by Ed operating over a wiper of C marked over bank f of CF in accordance with the conversation junction group between tandem and toll. At tandem S repeats the impulses over Lm to SM1 and when Lm relapses at the end of the train, Fd pulls up to switch the impulse circuit over to SM2 which receives the next digit transmitted in a similar manner except that it is determined by individual junction marking wires over bank e of CF. When Fd energizes, TF starts hunting'for the junction group marked over TF (a) and S1 (c), the hunt being stopped by T but when Lm relapses after the next digit Sd pulls up followed by Sf and T relapses. TF starts hunting for the particular junction marked over S2 (c) and is again stopped by T. The operation of Sf energizes Sp, Ak and Sr whereupon the grid of valve DV is connected over transformer GT and filter RC to a source of 125#. A.C. and anode relay A pulls up and operates So so that Sp, Sr and Ak fall back, the A.C. source being disconnected. The operations now differ according to whether the call originated at tandem or not. Call originated at tandem.-Contacts of bank b TF, Fig. 5, are connected to the 4th wires of local group selectors 1GS, Fig. 1, so that battery from Tt (5) connected to the b wiper by So starts the identification circuit IC at tandem. The grid transformer GT is now connected to the 4th wire circuit to which is also connected-a source of 450v. to mark the calling line in the identification circuit. After identifying the line, the circuit first sends back, a pulse of 125v. followed by a spaced pair of pulses. The 1st pulse operates anode relay A followed by Fi and Tt which removes the identification start signal and on the relapse of A, Fh pulls up releasing Ic which is followed by the relapse of Fi and FA and the re-operation of Ic. The 1st pulse of the spaced pair operates in a similar manner' but before Fi and Fh can fall back, A re-operated by the 2nd pulse energizes Si which holds in series with Sh and removes the 450#. marking, Fi and Fh remainihg held.. Relay Sh completes a circuit from,the 450 #. source to transformer ST under the control of A so that the number of the calling line comprising succeeding trains. of 125#. impulses from the identifying circuit is repeated in the form of 450#. impulses over leads 7, 8, group selector WNGS and the identification junction to transformer TTR, Fig. 2, at IL, Fig. 1, in the toll exchange. The impulses are thereafter repeated over the 4th:wire and TIGS to the control circuit TC of the ticketing machine. Call originated at exchange A.-Switch TF of circuit IT (tandem) is connected over ENGS, Fig. 1, so that when So operates,-ground over Ij is connected over the b-wiper in this case and the 4th wire to operate Mt, at circuit IL (tandem). This circuit operates in the manner previously described for IL (toll) to set up an identification connection over a junction to A where IT is set to the conversational circuit and calls for and receives the identity as previously described, and repeats it to circuit IT (tandem). The latter circuit does not now require the preparatory 125#. pulses. Ij has operated in the circuit mentioned above, and is followed by Ih, whereas So releases Sp and Sr during the release period of which Si and Fi pull up and lock in series with Sh and Fh. The 4th wire from wiper d, Fig. 2, at IL (tandem)-is now connected over wire 2, Fig. 5, at IT (tandem) to transformer GT so that the identifying impulses from IL are repeated by relay A over transformer ST to the toll exchange as previously described. Release of identification circuits.-When circuit TC at toll has received the identity, it releases Mt (Fig. 2) at IL (tandem) followed by Ct, Ch, Cb and other operated relays. Switches C and D go home and the junction circuit OJC, Fig. 4 is released followed by incoming, selector WNGS and removal of ground from wire 9, Fig. 5, in circuit IT (tandem) whereupon this circuit-releases and homes its switches. Busy conditions on identification route ; priority for identification.-If all junctions of the group are busy, a chain circuit over contacts of relays S1, Fig. 4, operates group relay Oc, Fig. 3, which holds both over Ss (operated) and Sb (unoperated). Relay Ab, Fig. 4, thereupon pulls up to open the normal test circuits of the junction group so that an idle one cannot be seized for conversational purposes. When a junction becomes idle and is seized by JF, relay Oc is released followed by Ab which renders other junctions available for conversation.