Patent GB-307959-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone systems and apparatus
IPC: H04Q3/42
Filed: 1927-12-13
Abstract: 307,959. Standard Telephones &. Cables, Ltd., and Gould, J. R. Dec. 13, 1927. Semi-automatic exchange systems. - A B- operator by pressing the assignment key ASK of an incoming junction closes a chain circuit to the first idle link of a series 1 - - 4 (only 2 is shown in full). which finds an idle sender and connects it to the key-strip at contacts of relay KK. The chain circuit includes back contacts of relays SJ, KK of all links, front contacts of relays PY of busy links, and springs of a disconnecting key ODK individual to the selected link. Relay SJ is energized at the first seizure of a link and KK as soon as a sender is found; both these relays are unlocked as soon as the wanted number has been, keyed, while PY is energized from this moment until sending is completed. The same switch DD, Fig. 2, puts the relay groups M, C, D, U successively under control of the key-strip and later gives them successive control of sending. Wrong numbers are cleared down by a key C. Normal operation. The B-operator assigns a junction by pressing key ASK, and relay AS energizes and looks. If the A operator has already seized the junction, line relay L connects interrupter lead FR to flash the junction lamp JL; this circuit is opened by relay AS. Ground applied to the start circuit at contact AS7 now energizes relay SJ of the preselected link circuit, and the switches JF, SF operate in search of the assigned junction and an idle sender respectively. Relay KS energizes when an idle sender is found, connecting up switching relay KK. which lights lamp JL and locks relay KS. Relay KJ energizes when the junction is found. Relay B pulls up, removing ground from the start circuit and releasing relay SJ. Relay BG- energizes over wiper P, starts the motor and connects up relay SZ. Operation of a digit key connects ground over wipers W-Z and wipers of the switch DD to one or more of the thousands storage relays M in series with relay DS. The operated relays lock, and on release of the key, relay DS falls back and the switch DD advances one step to connect up the hundreds storage relays C for operation. The remaining digits are registered, and in position 5 of the switch DD, relays SS, PY energize in series, the former locking and closing the out-impulse loop at contact SS2, the latter releasing relays SJ, KK, KS. Wipers X, Y are now connected to the trunk leading to the first group selector, and the link circuit is held by ground over wiper W. Lamp JL is extinguished, meter PM is operated, and the start circuit is extended to the next link circuit. When the A-operator seizes the junction, line relay L energizes and relay ST energizes over wiper Z, locks and disconnects relay SZ. Ground returned over the test wire of the first group selector holds relay B and energizes relay D. Meter AM registers an effective call. Relay CC energizes over impulse springs MGS, and connects these springs to the magnet of the switch MS. Start relay SA energizes and removes a short-circuit from the out-impulse loop, and impulses are sent from the impulse springs LS until wiper S2 of the switch MS reaches the terminal marked by the thousands storage relays M, when stop relay SZ pulls up and releases relay CC. The switch MS moves to normal by self-interruption, relay RA being energized meanwhile to give an alarm if the switch sticks. Relays SA, SZ fall back in turn, and an impulse is sent to advance the switch DD one step to render the hundreds storage relays C effective for the next digit transmitted. After the last release of relay SZ, relay BQ pulls up in position 9 of the switch DD, locks, disconnects relay BG and flashes lamp SP to denote clear-down. The switch DD restores to normal, and the operated relays are released. Relay AS falls back, and the connection set up is placed under control of the A-operator. On reply of the called party, relay D energizes and connects up the battery winding of line relay L to give supervision. In the case of a busy condition, busy flash is repeated by relay I through relay L. Cancelling a wrong setting. Cancel key C causes the operation of the X and Z relays of the storage group connected up at that time, and these provide a circuit for relay BQ to restore the sender to its original condition. Settings comprising less than the full number of digits. Start key S is operated in this case to energize the W, X and Z relays of the storage group connected up at that time, and a circuit is closed for advancing the switch DD to position 5 to start impulse sending. After the number has been sent, this setting of the storage relays causes the energization of relay BQ to clear-down the apparatus. Incomplete setting. Assuming that the switch DD stands in one of the positions 1-4, when a fresh junction is assigned by the B-operator, ground on the start circuit energizes relay MB, which connects up relay SS, and disconnect the storage relays and relay SZ. If the junction has not been seized by the A-operator, relay BQ energizes and clears down, but if the junction has been seized, relay ST energizes and a sending operation takes place under control of earthed terminals MS 11-14, which are jumpered to terminals 1-10, 15 to route the call to an operator, relay BQ being energized over terminal MS 15 to clear down after any desired number of digits. If on the other hand, a fresh junction is not assigned in a given time, alarm relay TP energizes and connects up relay MB, and the operation continues in a similar manner. Junction not seized in a given time. Alarm relay TP energizes and connects up relay MB to clear down. All senders of a group busy. A chain circuit SC is completed over contacts of relays BQ, BG for energizing the relays PY of all link circuits serving the group not associated with a sender. The next link circuit is thus preselected at each position. If relay SJ was energized at this time, it falls back and the assignment passes to the next link circuit. Disconnect keys. Key ODK serves to cut out a link circuit, the start circuit being extended to the next link circuit, while BK serves to mark a sender busy. Key SK when operated lights lamps SP of all busy senders.