Patent GB-360354-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1930-04-22
Abstract: 360,354. Automatic exchange systems. JACKSON, L. MELLERSH-, 28, Southampton Buildings, London.-(Telefonaktiebolaget L. M. Ericsson ; 33, Kungsgatan, Stockholm.) April 22, 1930, No. 1096. [A Specification was laid open to inspection under Sect. 91 of the Acts, Jan. 13, 1930.] [Class 40 (iv).] Amplified inter-exchange connections are established at a semi-automatic position, Fig. 1. over link circuits SL each comprising a pair of selectors LVI, LV2, and an amplifier FA. The selectors are both set numerically by impulses transmitted over a call-finder AS and a supervisory line KL from an operator's equipment E P, the selector LV1 being set to the actual junction IL1 over which the call has arrived, whilst the selector LV2 is set numerically to the first junction leading in the required direction and then hunts, if necessary, until an idle junction IL2 is found. The selectors LV1, LV2, and the call-finder AS are of the rotary and radial power-driven type described in Specification 176,065, [Class 40 (iv) Telephones &c.], the selectors being controlled successively by a single register RE which responds to both numbers. If the selector LV2 reaches the end of a group without finding an idle junction, its motion is reversed and during its return movement it may stop on a busy junction and wait until it becomes free. If all the junctions are busy and also have selectors waiting to seize them, a busy signal is given. The junctions are provided with compensating networks LF and with balancing networks B which are connected up over extra wipers of the selectors LV1, LV2. Detailed operation, Figs. 2-5 ; connection over finder AS to link SL. When a call arrives over junction IL1, relay IR1 lights lamp L1, and the operator throws key EO1 to establish a talking connection with the calling junction, key BK1 which marks the control circuit UL1 in the banks of finders AS, and key SK1 which marks the group contact Kd and through relay LRG starts the finders. Key BK1 also operates relay RL2 which by disconnecting the lower winding of relay RL3 marks the junction IL1 busy to the switches LV. When the group contact Kd is reached, relay RS4 operates over circuit 10 moving sequence switch SOS to position 3. The finder now moves radially into the selected group and when the marked individual contact Kc is reached, relay RS4 operates again over circuit 13 moving SOS to position 4 in which relay RS6 operates to connect the a- and b-wires to the register RE and switch SOS moves to position 5. A dialling signal is transmitted over relay RR4 to the operator who dials two three-digit numbers, one corresponding to the actual junction IL1 and the other to the first junction in the wanted direction. During dialling relay PR is operated over off-normal springs 15 and locked over the a-wire, impulses being transmitted from springs 17 over the b-wire to relay RR4. Selector LVI. In position 5 of SOS relay RG1 operates over circuit 18 and locks. When the register has been completely set, negative battery is extended over conductor 20 to operate relay RG2 which advances sequence switch SOV1 to position 2 in which the magnet CVG and clutch MHG are connected up for the rotary motion. During this motion reverting impulses are sent over interrupter 21 to relay RR7 and when group selection is completed, relay RR8 opens circuit 20 releasing relay RG2 which advances SOV1 to position 3. RG2 again operates moving SOV1 to position 4 in which magnet CRG and clutch MHG are operated for the radial motion and reverting impulses are sent over interrupter 22. When line selection is complete, relay RR8 releases relay RG2 to advance SOV1 to position 6 in which test relays RG3, RG4 operate and the sequence switch moves to position 11. Relay LFR operating in the test circuit releases relay RL2 whereby relay RL3 operates to connect the junction IL1 to the bank of switch LV1. At the same time lamp BL is extinguished. Selector LV2. When line selection in selector LV1 is completed relay RR9 advances switch SOS to position 6 in which rotary and radial setting of selector LV2 takes place in a similar way, after which relay RR10 operates and SOS moves to position 9. In position 6 of sequence switch SOV2, test relay RV3 is connected up and if the junction selected is idle, RV3 operates and advances SOV to position 11. If the selected junction is busy, a new circuit for magnet CRV is completed and the switch LV2 hunts. If no idle junction is found the wipers move to last contacts S2 in which relay RV5 operates over the test wiper energizing a relay RV4, disconnecting RV3, and connecting up a new test relay RV6. Relay RV5 also moves SOV2 to position 7 in which magnet CRV and the reverse clutch MVV are energized. The switch wipers are thus returned over the group, relay RV5 releasing and advancing SOV2 to position 8 as soon as contacts S2 are left. During this return movement, if a junction is found which is busy but has no other selector waiting on it, relay RV6 operates advancing SOV2 to position 10 in which RV4 releases connecting RV3 again to the test wiper. The operator is notified of the waiting condition by the intermittent operation of relay RF2 over interrupter UB producing a cracking noise in the receiver, and by throwing key E01, this signal may be caused to flash lamp L2 through relay IR2. As soon as the junction becomes free, RV3 operates and advances SOV2 to position 11. If all the junctions are busy and have selectors waiting the selector LV2 moves back to contacts S1 preceding the first junction and in this position relay RV5 operates and moves SOV2 to position 9 in which a busy signal from circuit 23 by induction through circuit 24 is transmitted to the operator. Completion of connection through amplifier FA; ringing. When both selectors LV1, LV2 reach their 11th positions, relay RF1 operates completing a circuit for relay RF6. A circuit 36 over the differential upper winding of relay RL3 releases this relay so that junction IL1 is again temporarily connected to the operator's position and the calling exchange is rung by operating key RO1. At the same time the wanted exchange is rung by operating key R02 which energizes relay RF5. When both have replied, key EO1 is restored and relay RF6 releases, whereupon relays RF7, RF8 operate to complete the talking connection through the .amplifier FA. Release. A clearing signal operates relay RF9 or RF10 completing a circuit for RF4 which locks over the b-wire and energizes IR2 which lights lamp L2. The restoration of key BK1 releases relay RS4 to return switch SOS to normal. Relays RG1, RV1 release causing switches SOV1, SOV2 to move to their 12th positions in which restoring circuits are successively completed for the radial motion, the rotary motion, and the advance of the sequence switches to position 1.