Patent GB-528690-A (GB)
Title: Improvements in or relating to electrical signal storage equipment
IPC: H04Q3/00
Filed: 1939-05-02
Abstract: 528,690. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., HARTLEY, G. C., and GRIFFITH, G. D. H. May 2, 1939, No. 13106. [Class 40 (iv)] In a key-sender in which the digits are registered on groups of condensers, an additional set of pilot condensers is provided to record the number of digits registered in order to effect immediate release when all the registered digits have been sent. Impulse transmission takes place under the control of a chain of counting relays which also determine the length of the interdigital pause. Registration. When a key is depressed, DK, CA energize, followed by ST which brings about the closure of the outgoing loop LP and holds thereover. Relay ST locks CA and connects up AA, M to operate the first relay A of the relay chain A-H which brings the condenser groups CG 1-8 into use in succession. Relays BB, BR serve to connect up the odd and even groups alternately to avoid sharing of charges and are controlled on the release of each key by the relapse of DK, Relays A-H operate one at a time over back and front contacts of BB alternately. For each digit, one of the five condensers of the appropriate group receives either a positive or a negative charge. Impulse transmission. Relay SF energizes over a contact of H if the full eight digits have been keyed, or over the sending key. Relay DS energizes, locks and operates SS, which connects up M to restart the relay chain A-H. Relay ST remains held by SF. Impulses are sent over the loop LP by relay I under the control of a vibrating relay VB of the kind described in Specification 516,386. Counting relays W-Z are operated by the reversals of the charge on a condenser QA produced by the vibrations of contact i3 and connect the five condensers of a group in turn to a pair of test relays N, P associated with rectifiers, the order of operation being X ; Y ; Z ; Z, X ; Z, X, Y. If a negative charge is found, N operates, followed by NN which disconnects W-Z and connects up K. Relay ID operates to shortcircuit the loop LP, L pulls up and NN falls back. If a positive charge is found, P operates, followed by PP which conditions W-Z for counting five more impulses, the order of operation being W; W, Y; W, Z ; W, Z, X ;  W, Z; X, Y. At this point, a circuit is made for N which brings about the operations stated above. When NN falls back, relays W-Z start to count ten impulses to provide the interdigital pause. At the fifth impulse P, PP operate over YC and connect up DK which by its relapse controls BB, BR and the relay chain A-H. At the tenth impulse, a circuit is made over YD for N, NN which bring about the release of K, ID and the initiation of the next digit. Release. The eight pilot condensers SC are connected in succession by BR and A-H to a charging battery during registration and to relay Q during impulse transmission, so that this relay energizes for each digit registered. When a condenser group is reached on which no digit is registered, Q fails to energize and ES operates when NN is up at the end of the inter-digital pause and unlocks CA, SF to effect release. The condensers are discharged by a momentary operation of CB, CC. Relay ES serves to effect release when the sending key is depressed before any digit is registered and when the cancel key is depressed.