Patent GB-520476-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone or like exchange systems
IPC: H04Q3/00
Filed: 1938-07-18
Abstract: 520,476. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., and PETERS, G.E. (Kozma, L., and Simon, S., in part). July 18, 1938, No. 21305. Addition to 484,647. [Class 40 (iv)] In a system in which, as in the parent Specification, alternating current line-marking wires are connected in groups through isolating condensers to common points connected to group-marking wires, earth is connected to the appropriate common point during line selection. This enables the same marking to be used for both selecting operations. In one arrangement, Fig. 1, an identifying circuit IC on receiving a starting signal over a wire SL from a distant exchange causes a switch CS to select a line ML over which it sends alternating marking current which passes back over the junction to the marking wire of the calling line. This marking wire is connected through an isolating condenser CN with a group marking wire which it shares with the other lines in the same level of the up- and-around final selectors. Switch GF hunts for the group marking and so selects a latechoice final selector FS modified to act as an identifying switch. The latter is then set to the level denoted by the position of GF and then hunts for the A.C. marking, the common point being grounded meanwhile. The setting of FS is registered in the apparatus IC and the appropriate digits of the calling number are then sent to the distant exchange. In another arrangement, Fig. 3, for a system using 200-line rotary power-driven switches, the A.C. marking is applied at the outgoing junction circuit. A switch IM in the indentifying circuit having 100 positions and five sets of wipers hunts for the group-marking which corresponds to the 20 lines reached over a particular wiper set of the final selector. Each final selector group occupies two adjacent positions in this switch. Switch IF then selects the first idle one of two last choice final selectors modified to act as identifying switches in the group determined by the setting of IM. The appropriate wiper set of this switch is tripped in accordance with the position of IM and it then hunts for the A.C. marking, the common point being grounded meanwhile. The appropriate digits of the calling number are registered in and subsequently transmitted from the apparatus IC. A further arrangement not described in detail is the same as that shown in Figs. 7 to 10 of the parent Specification except that single frequency marking is used and the common points are grounded during line hunting. First system circuit arrangements, Fig. 2. On the reception of the starting signal, relays ST, STR pull up and sequence switch SS is driven to position 2 in which CS hunts for the marking on ML. The switch is stopped by T which energizes TT and the sequence switch then moves to position 3 where it energizes LC if the other identifying circuits are idle. LC locks and energizes LD which applies the identifying frequency to the calling circuit via ML, Fig. 1, and drives the sequence switch to position 4. In this position GF hunts for A.C. marking under control of V which on operating to stop GF energizes' FC which drives the sequence switch to position 5 and grounds the common point to which the group marking wires are connected. In position 5, S pulls up and is followed, on the next opening of springs INT, by SD, ID. The subsequent closure of the springs energizes IR which then delivers impulses to magnet VM of the identifying final selector FS and to the driving magnet of switch SM until the latter reaches the terminal marked over gf 5. Both switches are then stopped by DC which locks and releases SD. Switch SM then goes home and shunts out DC whereupon the sequence switch moves to position 6 in which RS reenergizes S. Impulses are now delivered to the rotary magnet RM and the magnet of switch SM until the test wiper of FS encounters the A.C. marking whereupon V pulls up to stop it and the sequence switch moves to 7 in which LC, LD, V fall back,and FG pulls up. The sequence switch then moves to position 8. IR also delivers impulses from a condenser to a relay chain RA ... RE which builds up to RE, each relay unlocking the preceding one for the first five impulses and builds up again in a similar way but with RE locked for subsequent impulses up to the ninth. In position 8 S pulls up again and impulses are sent out over.CSM2 to the storage circuit and simultaneously to switch SM. which stops the digit by energizing DC when it reaches the position marked by GF. SM then goes home, the sequence moves on and a further digit is sent in a similar way. The final digit is sent in accordance with the marking applied by the relay group RA to RE and the circuit then returns to normal.  Second system circuit arrangements, Figs. 4 ... 6. On the reception of the starting signal relays St, Op, Mf, Oc, Vo, Fc, Bc, Id, If, Sb pull up, and the input transformers of valves DV1...DV5 are connected respectively to the test wipers a ... e of switch IM and' the power magnet IMM is energized over back contacts of the anode circuit relays A1 ... A5. Mf falls back shortly after the operation of BC and energizes the power magnet IFM. Switch IF then chases IM under control of F@. When the A.C. marking encountered one of the anode relays stops the switch IM and Ar, Ao pull up in turn. Mb is thus connected momentarily to IMg and if another switch is in the same position drives IM on again. In the normal case however Ao is is followed by Mt, Dt, Oh. When switch IF catches up, it may be stopped by Ft in either of two positions according to the busy or idle condition of the identifying final selectors in the marked group. Oh starts the switch CM in search of the junction circuit under control of Ss which pulls up in due course in series with Tpr, Fig. 3, which removes the starting signal. Df is operated at the same time as Ft and is followed by Fp, Dm. Fp completes the fundamental circuit over wiper IFa and Os, which repeats the reverting impulses to relay X and switch T during rotation of the trip-spindle. The condition of Ob, which is operated if the wipers of IM are in a position indicating the first five levels in the final selector, determines whether level register T shall test for the operated A relay in its first or its second group of 5 terminals. When this A relay is reached, Fo releases Fp, opens the fundamental circuit and energizes Ts, Tb. On the relapse of Dm resulting from that of Fp, driving magnet DM is released to allow sequence switch D to move to position 2. The relapse of Bc on the operation of Ts re-energizes Mt and releases the operated A relay. Relays Fo', Ar, Ao fall also. Sequence switch D moves automatically to position 4 in which it re-operates Fp and energizes Us. The fundamental circuit is thus completed again and final selector advances, Os repeating the reverting impulses to magnet UM of the line register. Ground on tmd is connected to the wiper a .. e of IM corresponding to the calling group to prevent alternating marking current applied to one lead from being picked up from another. When the final selector reaches the marked line, the A.C. marking via wiper c of IF reaches the transformer DT1. A1, Fo operate and Fp is released to open the fundamental, circuit and operate DM and release Dm. The sequence switch D then moves to position 5 and then automatically to position 6 in which an impulse sender DIF is started up and Lf pulls up energizing Ho, So and releasing Id which releases If to operate Sc, Cc. 450-cycle current is thus connected to wiper c of IF and this causes the disconnection of the marking tone. Cc releases Se which, after a brief interval, cuts off the 450-cycle current. At the same time transformer DT1 is disconnected and A1 falls releasing Fo. Oh, Ss are released also and a homing circuit is made for the sending switch C which, on reaching normal, causes the operation of Ic, Id, If. Impulses are thus delivered from DIF to Is which repeats them to magnet CM of the sending switch. The latter in position 2 energizes pick-up relay On which completes an A.C. impulsing circuit from the 450-cycle source and wiper c of IF. The digit sent is determined by the jumpering of terminal P to bank cmc over which relay Ed is energized in due course to stop the digit by disconnecting the impulse relay. Ed also energizes the sequence switch magnet and releases Ic which restores the sending switch and causes the relapse of Id, Ed, If, On. On the relapse of Ed the sequence switch moves on and the 10,000 digit is sent in accordance with the jumpering of point Q. The thousands digit is sent in position 8 in accordance with the terminal with which wiper f of switch IF is in contact. In position 9, Ad is operated and grounds wiper e of switch IF, the position of which jointly with that of the units register determines the hundreds digit. The terminals in this bank are strapped to bank cmb for odd hundreds digits and to bank cmc for even hundreds digits, the marking to become effective depending on whether wiper umb is on the first or the second half of its bank. The tens and units digits -are sent in accordance with the position of wipers tmc, umc. In position 12 the sequence switch shunts out Op to release the circuit.