Patent GB-471764-A (GB)
Title: Improvements relating to telephone systems
IPC: H04Q3/42
Filed: 1936-03-20
Abstract: 471,764. Semi - automatic exchange systems. SIEMENS BROS. & CO., Ltd., HENSLER, B. A., and HUMPHRIES, H. E. March 20, 1936, No. 8378. [Class 40 (iv)] In a system employing register-senders, a group selector failing to find an idle outlet in the wanted group performs a predetermined number of further searches at timed intervals which are measured by apparatus in the register-sender or in a common control circuit associated with the selector. Such apparatus may comprise the sequence switch of the register-sender which makes a complete revolution between the searches or a number of relays which operate cyclically under the control of time pulses in the manner described in Specification 221,316, [Class 40 (iv)]. The invention is described with reference to a system in which long-distance calls are set up over first and second trunk selectors at the originating exchange under the control of register-senders which are in turn controlled from an operator's keyset. The register senders include provision for alternating routing if the direct route is unavailable. Specifications 443,220, 465,011, and 468,722 also are referred to. Operator's circuit and first trunk selector, Figs. 1, 2. The operator assigns a link circuit terminating in a first trunk selector by throwing speak key SPK and position key CAK, thereby connecting up relays SK, SL in the link and MN, CG in the position circuit. If there are calls waiting, CN operates over ,wire CLD in series with a relay which starts a call distributer hunting for the assigned link. Relay B energizes in series with the test relay, disconnecting CG, CN, and connecting up AS. The operator learns the connection required I and presses key SCK to energize C, which connects up the code marking relays AWAZ and earths the sender start wire IN, and lights lamp GSL. Relay ST, Fig. 4, operates in a chain circuit and the sender becomes associated with the position circuit over a hunting switch, whereupon SP energizes and lights lamp SEL. The operator keys the exchange and numerical digits, and when these are registered earth is returned over wire D to operate ST. If all the direcroutes are busy, earth is applied to wire C to light lamp GCL and buzz relay GT; if delay working is in force, the earth is intermittent. Relay ST disconnects SP, which ,connects the sender to relays A.W-AZ, operates SR, connects RE to wire Sand operates SD in the link. The latter locks over a low resistance winding, thereby preventing operation of any other SD relay, connects both sides of the link to the position circuit and connects up SE, K. One or a pair of relays AW-AZ are operated from the sender and apply a marking through test relay T, so that the first trunk selector hunts for an idle outlet to a second trunk selector. Relay T pulls up followed by TA and connects up switching relays H, HA, whereupon K falls back. The markings for the setting of the second trunk selector are applied over wipers 1-4. The operation of PP when the first digit has certain values sends a signal to the second trunk selector to discriminate between two groups of outlets. Further digits are sent from the sender in the form of loop impulses. After the last digit has been sent, ST is unlocked in the sender, and disconnects SD, SE and lamp SEL. Relay CS operates over wiper 5 when the second trunk selector switches through and disconnects lamp CSL. On restoration of speak key SPK, relays SK, SL are disconnected and the position circuit is freed. The connection is released by operation of key RK which opens the holding circuits of B, H, HA. Busy conditions. If the first trunk selector fails to find an idle outlet, it stops and switches through in the last position. Battery applied over wiper 3 operates a relay in the sender which connects up RE over wire S. Relays TA, H, HA are disconnected and the marking wires are opened. After a predetermined interval RE is released, and the selector performs a further hunting operation. If this is unsuccessful, a third search may take place after a further interval, or the sender may be released and a busy signal sent. If the second trunk selector meets a busy conchtion in a direct route, the call is stored and the sender is released. Lamp CSL continues to light and flickers when trunk becomes idle,.whereupon the operator again throws the speak key to initiate hunting. If an indirect route is involved, battery over wiper 3 brings about the operation of RE and the release of the selectors. The sender retransmits digits indicative of the direct route and, since this is congested, the call is stored by the second trunk selector. Setting up a connection on the answering side. Key SAK is thrown in place of CAK, and relay A operates instead of CG. In the link circuit, RC, RS energize and earth start wire RST to associate a revertive first trunk selector, whereupon B energizes and connects AS to wire RSS. The number is keyed, and start key STK is thrown to operate ST. which sends a start signal over wire S to the sender to initiate control of the revertive trunk selectors. If further digits are required, a dialling signal is received and the operator dials the remaining digits. Register-sender, Figs. 3-6. Relay C is operated when the sender is idle, and a starting signal connects up ST, whereupon the switch SC rotates into association with the marked position circuit, and TC energizes. Relay SH is operative while the switch is off normal, and ensures that it will advance to normal if the start signal is removed. Earth is fed over wire P to operate SP, Fig. 2, and B, BA pull up, disconnecting C, ST. The sequence switch DD steps to position I in which wires W-Z are connected to register relays AWAZ. Assume first that the direct route is available, and that the operator keys the two appropriate digits, followed by a third digit 1 which causes the second trunk selector to hunt. Relay DS energizes in series with the register relays and on falling back when the key is released advances DD one step. After keying therefore, three groups of relays are set, and DD is in position 4. In position 3, CS energizes and advances the translating switch CM to a position marked by relays AWAZ, BW-BZ, whereupon T, CT pull up and connect up AS provided delay working is not in force and DG is inoperative. Earths is applied to wire D to operate ST, Fig. 2, which subsequently holds over wire P, and SR, S pull up. Relay PY energizes and DD moves to position 7 in which wires W-Z are connected via a distributing frame to the banks of the switch CM, certain wipers of which are connected up by PY. The digit for setting the first trunk selector in the direct route is marked in' banks CM1, 2, and that for the second trunk selector in banks CM3, 4. The corresponding digits for an alternative route . are marked in banks CM 5-8. At the present time, relays TT, TS energize over CM1, 2 in series with marking relays in the position circuit, and fall back in turn when the first trunk selector is set, connecting up DS momentarily so that SS, RL are connected respectively to wires Z, Y. DD advances to position 8 in which the setting of the second trunk selector is controlled in a similar manner and then to position 9 in which a marking corresponding to the digit 1 causes the second trunk selector to hunt. Relay CO energizes in position 10, opens wire P to signal the completion of sending and initiates release. If the second trunk selector is required to select a particular trtmk, the third digit is 2-0, and a corresponding marking is applied. If the direct route is available, PY energizes over wiper CM10 when the switch CM is set; if however all direct trunks are busy but an alternative route exists, SY energizes in place of PY, wipers CM5-8 are effective instead ot CM1-4, and a signal is sent to the operator over wire C. If the second trunk selector finds the alternative route busy, battery on wire Y energizes RS, which earths wire S to release the selectors and causes DD to step through normal to position 7 in which PY pulls up and disconnects SY. An attempt is made to set up the call over the direct route, and since this is not available, the call is stored and the sender is released. If neither route is available, PY energizes and the call is stored in the same manner. If the first trunk selector finds no idle outlet, battery on wire 7 energizes RL, which earths wire S to release the selector and places DD under the control of a condenser-timed pulsing relay Y. After 2¢ sec., DD again reaches position 6, in which RM energizes and disconnects RL, Y, and DD moves to position 7 in which the control of the first trunk selector is repeated. If there is still no idle outlet, battery on wire Y energizes CO to release the sender. If delay working is in force, the relevant positions of CM9 are earthed by keys and DG operates, signals to the operator over wire C and prevents the operation of AS. If the first two digits keyed constitute a dead number, T, RM operate in the last position of CM, the first trunk selector hunts without result and sends a release signal over wire Y. The second trunk selector hunts without result in a similar way if the third digit corresponds to no trunk. Local call. The first digit 1 is followed by four numerical digits. The setting of AWAZ prevents the operation of CS, the translating switch CM is ineffective, and sending is delayed until all the digits are registered. DD is then in position 6 and AS, SR, S energize to start sending. If there are less than four digits sending is initiated by the operator's start key. In position 7, the first trunk selector seizes a first numerical selector, and battery returned on wire Z energizes SS which loops wires W, X and advances DD to position 11. The banks of switches SM, SN are now marked by the register relays, and SX energizes and connects up pulsing relay Y, which delivers impulses over the loop and to the switch SM. Stop relay SZ energ