Patent GB-232702-A (GB)
Title: Improvements in or relating to semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1924-01-28
Abstract: 232,702. Automatic Telephone Manufacturing Co., Ltd., Bennett, A. F., and Gillings, C. Jan. 28, 1924. Semi-automatic exchange systems.-In a. system in which trunk connections are set up by an operator over a cord circuit by means of an impulse sender, the operator presses a key 1 corresponding to the required exchange whereupon her impulse sender 38 which is of the dial type is connected over a hunting switch to an idle trunk 42, 43, and a lamp 22 is lighted to indicate which trunk to plug into. The invention is intended to apply particularly to multiexchange systems in which the exchanges are gradually being converted from manual to automatic working. Preferably a separate switch is employed for each exchange, but a single switch having access to trunks to several exchanges may be used. The operator's dial 38 is such that impulses are sent at each closure of the impulse springs, and these are repeated over the trunk at contact 41 by a relay 23. The apparatus may be modified to send impulses directly over the trunk. According to the Provisional Specification, a keyboard impulse sender may be employed. A relay 62 normally energized over a chain of contacts is provided to prevent the impulse sender becoming associated with more than one trunk. Circuit arrangements. Relay 2 energizes over key 1, locks and connects up the magnet 10 of the hunting switch in series with relays 7, 8 which remain short-circuited over test wiper 13 until an idle trunk is found, and then operate to mark the trunk busy, light lamp 22 and connect up the operator's dial 38. The operator plugs into the selected trunk, and relay 26 energizes, connecting up bridge relay 33 and placing a further ground on test terminal 19. Dialling now takes place, and at the first energization of relay 23, relay 36 operates and at contact 45 closes a direct bridge across the trunk. A two-step relay 47 partially operates over off-normal contacts 40 and at contact 49 connects up its lower winding, which is short-circuited at contacts 40 until the end of the impulse train, whereupon relay 47 operates fully and transfers the energizing circuit to a similar relay 50. Relays 50, 51, 52 operate in the same way, and at the end of the fourth train, relay 54 energizes and removes earth from relays 2, 7, 8 to release the apparatus. Since relay 8 falls back before relay 2, a momentary circuit is completed for magnet 10, which advances the switch one step. The impulse sender may be released at any stage by means of a key 61 which controls relay 54. Relay 62 is held over resistance 63 when key 1 is pressed, contact 14 being opened. If another exchange key is pressed, a second resistance is inserted in the circuit, and relay 62 falls back and releases the apparatus. The single lamps 22 may be replaced by tens and units lamps, and may or may not be multipled to the various operators' positions. Busy signal. Battery and earth are connected alternately to wire 43, and the first battery releases relay 33 and connects up relay 34 which locks. Relay 33 then energizes intermittently, causing lamp 27 to flash by earth over contacts 35. 65.