Patent GB-380527-A (GB)
Title: Improvements in or relating to automatic switches for use in telephone or like systems
IPC: H01H63/20
Filed: 1931-06-22
Abstract: 380,527. Automatic exchange systems and switches. AUTOMATIC ELECTRIC CO., Ltd., Strowger Works, SAVILLE, W., 35, Thingwall Hall Drive, Broadgreen, WOODHEAD, H. S., 23, Watergate Lane, Woolton, SHARPE, H. D., 181, Warbreck Moor, Aintree, and McGAVIN, J., 15, Zigzag Road, West Derby, all in Liverpool. June 22, 1931, No. 18089. [Class 40 (iv).] To ensure full operation of the stepping magnet of a switch on distorted impulses, the magnet armature, when it begins to move, closes springs which maintain the magnet circuit until a full operation has been made. The magnets of the switches are connected direct to the speaking leads and an impulse responding relay is provided at the first selector only, this relay breaking its own circuit on deenergization during impulsing and being prevented from re-operating until the magnet has been fully energized. The invention is described as applied to first, intermediate and final selectors and to an incoming selector, ringing and feeding currents being provided from the first selector. Booster battery metering is provided. In the intermediate selector one switching relay is used as a change-over relay whilst the other is used to open the release magnet circuit when the switch is seized. Construction of magnet armature. Figs. 5 and 7 show suitable mechanical constructions for.operating the contact springs of the vertical and rotary magnets of a bidirectional selector. When the vertical magnet is energized the pawl 37 moves upwards and by means of extension 36 it turns the member 31 about its pivot 32. The spring 35 prevents the wheel 33 from, rotating in a clockwise direction so that 40 rides up a tooth and closes contact springs 39. When the magnet has fully energized, spring 40 will pass over the tooth, springs 39 open and the magnet de-energizes. Spring 40 now prevents the wheel 33 from moving clockwise so that as 37 falls and 31 moves clockwise into its normal position, spring 35 rides over a tooth on 33. Referring to Fig. 7, the arm 50 carrying wheel 51 is directly connected to the armature of the rotary magnet. When the magnet energizes 50 moves towards 57 and 56 rides up a tooth to enable 57 to close contacts 54. At the completion of the stroke 56 falls over a tooth and during the return movement of the armature the spring 53 moves into the next tooth position. Operation of first selector, correcting impulses. When the selector, Fig. 1, is seized over conductors 10, 11 relay A energizes and B pulls up. Relay B opens the energizing circuit of A, but A remains energized over its own contact. Relay J pulls up and locks. Dialling tone is returned over 1N1. When the first impulse of the first digit is received A falls away breaking its own circuit and completing circuits for the relays C and MS and for vertical magnet 1VM. When 1VM starts to operate it closes its contacts 1VT which remain closed until the magnet has energized fully. Relay MS has the same operating time as 1VM and energizes to recomplete the circuit of A only when 1VM has completely operated so the A cannot re-energize until 1VM has operated fully. The relay MS can be dispensed with and relay A made dependent on 1VM when A repeats impulses to 1VM only, but the provision of MS is necessary when relay A is used to repeat corrected impulses to further switches in the train. Relay A re-energizes after both the energization of MS and the termination of the break. Further impulses in the digit operate A, MS and 1VM in a similar way. B and C hold up during the train and, when this is complete, C falls away and 1RM is energized, over 1NR1 and 1N4, completing a local circuit for itself at 1RT to ensure full energization. 1NR1 change over on the first rotary step connecting 1RM to the test wiper P. If the line tested is busy, H is shorted by earth on P and 1RM reoperates. When a free line is reached H energizes in series with 1RM, disconnecting 1VM and switching through. If all outlets had been busy the switch would have rotated to its 11th position in which the upper line wiper is connected to earth over resistance 24. Relay H, being no longer shorted over P, pulls up and BB operates to connect busy tone to the calling line. Intermediate selector. If the intermediate selector, Fig. 2, is seized by the first selector, relay HB energizes over 13 sufficiently to close contact hb1 which opens the release magnet circuit. The next impulse series is repeated by A, Fig. 1, to 2VM, relay HA energizing in series sufficiently to open contact ha1 only. HA holds during the train and 2VM steps the switch to the required level, contacts 2VT being provided to ensure 2VM making a full step on each energization. When the train ceases HA falls away and 2RM energizes to step the wipers into the multiple bank. Springs 2RT ensure a full mechanical stroke of 2RM at each energization. Rotary off-normal springs 2NR4 open on the first rotary step of the switch and 2NR1 and 2NR2 close. The selector is provided with 2 sets of wipers and if both sets encounter busycontacts earth is extended from 2P and 1P in parallel to operate 2RM, and the wipers are moved a further step. The resistances 20, 21 ensure that 2RM will not energize if only one of the test wipers encounters earth. When a free line is reached the rotary magnet does not energize and the relative switching relay, HA or HB, energizes and switches through. If all lines from the level are busy, earth is returned over the conductor 14 to energize BB, Fig. 1, which returns busy tone to the calling subscriber and releases the intermediate selector. Setting of final selector, ringing, metering. Assuming that the final selector, Fig. 3, is next taken into use, relays VC and 3H energize over 23, relay H operating its contact 3h1 only to open the release magnet circuit. Relay VC connects the vertical magnet 3VM to the speaking conductors and the next impulse train is repeated to 3VM which steps the selector, contacts 3VT being provided to ensure full energization of 3VM at each step. On the first vertical step 3N1 open the initial circuit of VC but this relay is held during the impulse train in series with 3VM. When the vertical train ceases, VC releases and changes over the impulsing circuit to the rotary magnet 3RM which responds to the final impulse series. RC energizes in series with 3RM and holds up during the train. When the train ceases, RC releases connecting H to the test wiper 4P. If the line is busy the test wiper encounters earth which is extended over 3NR4 and the upper speaking conductor to energize BB, Fig. 1, which returns busy tone as before described. If the line is free H operates and locks, switching the circuit through to the called line. Relay H is made slightly slow to operate and during this period battery over resistance 25 is connected to the lower speaking conductor to energize LS, Fig. 1. Relay LS is shunted by a rectifier RCT1 which is arranged to oppose 'current flow in this direction. Relay LS locks up, connects the battery feeding relay DA across the speaking conductors and connects ringing current from GNR to the wanted line. Ring-back tone leaks back over QA. When the called subscriber replies F energizes to disconnect ringing and connect the parties together. Relay DA energizes to connect booster battery to conductor 12 for metering the call and the circuit of slow release relay J is opened. When J has fully released it disconnects the booster battery and replaces it by a guarding earth. Discriminating junction calls. The selecting switches, Figs. 1 and 2, are provided with normal post springs 1NP, 2NP which are closed on levels connected to outgoing junctions. When the line is switched through on one of these levels, relay JD operates and locks. Relay JD disconnects the busy relay BB and substitutes relay D, which is shunted by RCT2 to make it responsive to currert flow in one direction only, the direction being opposite to that required to energize LS. When the wanted subscriber at the distant exchange has been selected, the direction of current flow over the circuit is reversed and D operates, instead of LS, to control metering. Ringing is provided from the incoming selector at the distant exchange, the operation of which is similar to the selector shown in Fig. 1 and is illustrated in the Specification. If a busy condition is encountered at the distant exchange, the busy tone will be extended over the junction from the incoming selector at the distant exchange.