Patent GB-343138-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone exchange systems
IPC: H04Q3/42
Filed: 1929-11-13
Abstract: 343,138. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., WRIGHT, E. P. G., and HAIGH, L. B., Columbia House, Aldwych, London. Nov. 13, 1929, No. 34643. [Class 40 (iv).] A hunting switch associated with an outgoing repeater has access to groups of junctions leading in different directions and the determination of the group in which a junction will be selected is effected in accordance with the means of access over which the repeater has been seized. In the system shown, a repeater RP, Fig. 2, giving access over a hunting switch to junctions to two different manual exchanges or to two different positions at the same exchange is associated on being taken into use with a common register, Fig. 3, which records the four numerical digits of the wanted number. When a register is taken into use it becomes associated over a switch LM with a pre-selected link circuit LC, Fig. 4, and such link circuits are associated in turn with an order-wire OW in the wanted direction over a further switch OWM, thus ensuring that waiting calls are dealt with in strict rotation. When the order wire has been associated with a register the wanted number is announced over the order-wire by a common call-announcing mechanism CA and the manual operator on hearing this picks up any junction cord, Fig. 5, at her position and tests and connects up the wanted line. After a predetermined time interval the switch CFM, Fig. 2, hunts for the selected junction, and the order-wire and register are released. If the wanted line is busy, the operation of a busy key BK, Fig. 6, transmits a signal back over the order-wire causing the register and order-wire to be released and a busy signal to be sent to the calling subscriber. The repeater, Fig. 2, and register, Fig, 3, are taken into use from a preceding bye-path over two different means of access, the operation or non-operation of a relay JJ, Fig, 3, determining the selection of an order-wire in the appropriate direction, the transmission if required of a signal indicating the type of call, e.g. the word " tandem," and the hunting of the switch CFM over junctions leading in the required direction only. If split order-wire working is employed at the manual exchange, the name of the calling exchange is also announced. Seizure and setting of register and connection to order-wire. The testing circuit T for an idle repeater associated with an idle register leads from the bye-path over back contacts hr1, br1, kr1, in the repeater, and contacts b6 and normal contacts of wiper rm32 in the register. Relay A in the register operates over the bye-path and energizes relays B, BB. Discriminating relay JJ is operated in series with relav A for one means of access and if operated locks up and short-circuits its operating winding. When the preceding talking path is completed relay KR operates over lead H and connects the repeater to the register. Incoming impulses are repeated by relay A through relay C to the rotary magnet RM3. At the end of each digit the relapse of relay C completes circuits over wiper rm32, relay Z, and wipers rm33 .. rm36 for appropriate register relays MA .. MD, &c., relay Z which operates slowly causing the wipers to move to the next starting position 10, 20, &c. If the thousands and hundreds or tens and units digits are the same a circuit is completed in position 20 or 40 of switch RM3 for operating all the thousands or tens register relays whereby the word " double " will be substituted in the call announcer for the first of the two identical digits. In position 40 of switch RM3 after all the digits have been recorded relay E operates over wiper rm38 and closes the starting circuit for magnet LM of the link circuit LC, Fig. 4, allotted by distributor DM. When the register in use is reached relays H, TL, W, Y, operate and the distributor DM takes one step. Relay H completes a circuit dependent upon relay JJ for a starting relay N of an order-wire leading in the wanted direction. When the orderwire is free, magnet OWM is operated and the switch associated with the order-wire is stepped until the link circuit LC is found when relays P, PP, K operate, relay K connecting relay BB over wipers lm2, owm2 and the order wire in series with relay LN, Fig. 6, at the manual exchange. Announcement of wanted number ; completion of connection. When the lamp CL lights, the operator throws her listening key LK releasing relay BB. Relay SA is now able to operate over its left-hand winding and the pick-up cam of the call-announcer mechanism CA, remaining operated over its right-hand winding for one rotation of the mechanism. Over contact sa7 an announcement which may be dependent upon relay JJ, e.g. the word " tandem," or the name of the wanted exchange, may be made. Relay SA closes a circuit for magnet RM3 which on the release of SA steps the wipers to position 41 in which the thousands digit is announced. Similarly in positions 42, 44 and 45 the remaining digits are announced, a pause being introduced in position 43. The switch RM3 then continues to step slowly under the control of relay SA until position 50 is reached, in which relay SZ operates. Meanwhile, on noting the wanted number the operator has seized an idle cord, Fig. 5, and tested the wanted line. If idle, the insertion of the plug energizes sleeve relay S which marks the junction by connecting ground to the a-wire. The switch CFM, Fig. 2, is stepped without hunting over junctions leading in the unwanted direction by a relay G which completes a self-interrupting circuit for magnet CFM, relay G being operated over a contact of relay JJ and wiper cfm2 or cfm4 and grounded terminals corresponding to the other group of junctions. Hunting for the selected junction is initiated by the operation of relay SZ which releases relay W and on the subsequent release of relay Y connects the test relay M to the a-wire. If the junction engaged is unmarked relay W operates again and before the operation of relay Y gives an impulse to magnet CFM. Busy junctions are passed owing to the operation of relay G over wiper cfm2 or cfm4. When the marked junction is reached relay M operates, causing the energization of relays HR, BR, AR. Relays A, B, KR, E, fall back and the register, link circuit and order wire are released. Relay ER operates over the b-wire in series with relay L. A tone is connected up at contacts sz7 during the time the switch is hunting to inform the operator as to its duration. Ringing. Relay L connects relay R in the sleeve circuit and relay R supplies ringing-current to the called line. When the called subscriber replies relay TR operates removing a short-circuit from relay RR which operates in the sleeve circuit and short-circuits R to cut off the ringing-current. Relay CS operates over the called loop and connects battery over coil LL to the a-wire to operate reversing relay DR, Fig. 2. Wanted line busy. If the manual operator finds the wanted line busy, she operates key BK, Fig. 6, thus applying battery to both conductors of the order-wire to operate relav BT, Fig. 3. Relays BR, AR, Fig, 2, operate releasing the register and orderwire and connecting up busy tone to the a-wire. Standstill release. Circuits are completed over an A-pulse lead and contacts 0, 10, 20, 30 of wiper rm31 for relay BT which in turn connects a Z-pulse lead to relay E so that if undue delay occurs in dialling relays BR, AR [operate to release the register and to give busy tone. In position 50 of switch RM3 the A-pulse energizes relay Z over wiper rm32 and after an interval the Z-pulse operates relay BT over wiper rm31 so that if the switch CFM has not by this time seized the marked junction the register and order-wire will be released as before. Release. When the calling party hangs up relays AR, BR release, but relays DR, ER, HR hold up in dependence on the called end. When the called party hangs up, relays CS, DR, ER, L release and lamp SL, Fig. 5, is lit. Relay S maintains ground on the a-wire of the junction to hold relay HR operated until the plug is taken down.