Patent GB-630408-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1946-11-02
Abstract: 630,408. Automatic telephone exchange. TENCH, F. (Automatique Electrique Soc. Anon.). Nov. 2, 1946, No. 27952/47. Divided out of 615,505. [Class 40 (iv)] In a automatic telephone system provided with arrangements for including a repeater in a connection, a balancing network is included in each junction relay set and on an incoming connection the network is connected to a repeater over a switching device which also connects up an idle repeater, while on an outgoing connection, the junction balancing network is connected to the selected repeater over a second switching device associated with the repeater. As shown in Fig. 1, on an incoming call over the junction B at a tandem exchange, the connection is extended over contacts C1, C2 to the hunting switch FT, which connects up an idle register. If the received digits indicate a call for a local subscriber, the connection over FT is released, and the call is completed over the preselector IH. In the case of a call for a distant exchange not requiring the insertion of a repeater, a circuit, similar to that shown, associated with the wanted junction, will be taken into use by the register over a path such as A, contacts C1 being operated in the out-going junction circuit. If, however, a repeater is required, the register causes operation of contacts C2, C3 in the incoming junction circuit, whereupon FA hunts for the idle repeater REP preselected by D under control of the distributer DIS. The switch FA connects the balancing network BLN to the incoming side of the repeater and extends the speaking path over the attenuator ATR and through the repeater. Meanwhile the register controls selection of the outgoing junction, the relay set of which marks the banks of the switch TD, which thereupon hunts for the appropriate balancing network BLNA and associates it with the outgoing side of the repeater. Since the repeaters are all of the fixed gain type, individual attenuators are . provided for each junction in order to obtain the required output level. Detailed operation. Relay P in the junction relay set (Figs. 2, 3) pulls up to an incoming seizing pulse, followed by Sand AP, whereupon FT hunts for an idle 2nd selector, with which the relay set is associated by the operation of CN. This relay brings up M, during the operate time of which PA and RS pull up momentarily to send the proceed-to-send signal over the junction. The incoming impulses are repeated to the 2nd selector and thence to a register taken into use by it. Call to local subscriber. The register connects direct earth momentarily to the d lead, thus bringing up CH which prevents full operation of the two-step relay AM, and extends the loop to the local switch train, while CN falls away, releasing the 2nd selector and register. Release is under control of the called party. Through - call to distant exchange. The register seizes an idle junction to the wanted exchange and applies earth to.the b lead, thus operating relay A in the outgoing junction relay set, followed by RS and PA, which transmit a seizing pulse to the distant exchange, HA coming up to terminate the pulse and switch through the speaking leads. Operation of P to the proceed-to-send pulse brings up M, which connects the upper windings of A and AB to the a lead, thus signalling to the register to commence the transmission of the impulses which are repeated by RS over the junction. If no repeater is required in the connection, the d lead from the register to the incoming junction relay set remains disconnected, so that neither CH nor AM is operated, and the register is released at the end of impulse transmission. Insertion of repeater. If a repeater is required, resistance earth is applied to the d lead from the register and brings up AM (CH being inoperative), whereupon FA hunts for the next idle repeater (Fig. 4) preselected by the distributer (Fig. 5), MA pulling up on finding, followed by TM, TMA and T (Fig. 5). Relay TM, on the operation of T, signals to the register that a repeater has been taken into use, while TMA extends the connection via ATR to the repeater and connects up the balancing network BLN, EE operating over the simplex circuit. On completion of impulse transmission, the register connects earth to the b lead of the outgoing relay set, operating AB to mark the outgoing junction in the vertical and test banks of TD (Fig. 4), and to bring up TMB, which connects the balancing network associated with the outgoing junction to the appropriate contacts of TD. The operation of T is followed by that of ST, whereupon TD hunts over its vertical banks under control of PP for the marked level, FA coming up on finding to initiate hunting in the selected level. Relay FR pulls up to the marked contact, followed by CNA, which completes the connection of the outgoing junction balancing network to the repeater, ES operating over the simplex circuit to complete the speaking path. Relay FR also brings up FFA and releases T, so that the distributer hunts for the next idle repeater over switch D. The register is timed to release at a sufficient time after the energization of AB to ensure operation of TD, and on the release, AB relapses but A holds. The response of P to the called party answer pulse brings up RE, which reverses the battery connections to the incoming relay set. Release is under control of the originating exchange, the relapse of P in the incoming relay set bringing down A in the outgoing set, and a release pulse being transmitted over the outgoing junction during the release period of H.