Patent GB-297487-A (GB)
Title: Improvements in automatic or semi-automatic telephone systems
IPC: H04Q3/42
Filed: 1927-06-20
Abstract: 297,487. Standard Telephones & Cables, Ltd., Baker, J. H. E., and Chanter, A. J. June 20, 1927. Automatic and semi-automatic exchange systems. -In a system employing register-controllers of the code-translating type, the A-digit switches are connected in parallel multiple to groups of first code selectors instead of being available over hunting switches, the arrangement being such that each selector accessible over any particular line switch is associated with a different A-digit switch. When the register-controller releases after a connection has been completely established, the A-digit switch remains in use for a short time in order to test for the presence of busy flash on the junction outgoing from the first code selector, and if a busy condition exists, it effects the release of the succeeding switches as well as of itself. Specification 8800/14 is referred to. Normal call. When the first code selector is seized, line and release relays L, B pull up, and busy ground is extended to wire 104 to mark busy all the selectors multipled to the associated A digit switch. Relay K energizes, locks over wire 102 and connects up relay BA, which places a further ground on wire 104. Relay A energizes over wires 105, 108 in series with relay IA (upper), and connects up relay C, while relay MD energizes over wires 101, 102. Dialling tone DT is sent over wire 109, and the first set of imposes are repeated by relay L over wire 107 to the vertical magnet VA of the A-digit switch, sluggish relay CA being operated in parallel. Springs NA are operated at the first step and springs NP at the second step, and relay GA energizes. When relay CA falls back, the rotary magnet ROT interacts with relay GA (now connected to test wiper PRW) to find an idle registercontroller. Test and switching relay HA energizesl when this is found, connecting wire 107 to wiper PUW, wires 105, 108 to wipers -W, +W and alarm relav TPA to wiper TPW. Relay TA energizes and locks, disconnecting relay BA and applying a fresh ground to wire 102, and relay CA re-energizes. The remaining digits are repeated to the register-controller, and the first train of impulses sent out therefrom are repeated by relay A to the vertical magnet V of the first code selector, sluggish relay C being operated in parallel. When relay C falls back, relay A is disconnected from wires 105, 108 and connected to test wiper PW, and interacts with the rotary magnet ROT to find an idle junction. Test relay H upon energization connects the line wipers - W, +W to wires 105, 108. When all the digits have been sent out, the register-controller releases, and relay HA falls back. Busy test and release of A-digit switch. Intermittent ground from wire TL1 operates relay TPA in two steps. Relay IA (both windings) is now bridged across wires 105, 108, and falls back intermittently in response to busy flash in case of a busy condition being encountered, and breaks the circuit of relay CA, which opens the bridge across wires 105, 108 to release the switches ahead of the first code selector, and connects up the release magnet ZA of the A- digit switch. Relay TA falls back in the normal position and removes busy ground from wire 102. Pulse wire TL1 is extended to operate relay RA (in two steps) and relay M. Relay MD falls back, busy tone BT is connected to the calling line and relays K, H relapse. The rotary magnet ROT interacts with relay A to move the selector to the 11th rotary position, in which it remains until the calling party hangs up. If, on the other hand, no busy condition is encountered, relay CA remains energized, and relay RA energizes and disconnects relay K, which completes the talking connection and cuts out relay IA to release the A-digit switch. The reversal of line current when the called party replies operates polarized relay D, which disconnects relay MD to effect metering. Release. When the calling party hangs up, line relay L falls back and breaks the loop to the succeeding switches. Relay C (both windings) energizes and holds until after release relay B has fallen back in order to maintain the selector busy for an interval to allow release of the succeeding switches. If the called party hangs up first, lamp SL is lighted until the calling party releases. Operator hold. Polarized relay D is not operated, and relay MD remains energized, thus preventing metering. When the calling party hangs up, line relay L falls back, and relay I energizes over wiper +W in series with the operator's supervisory lamp, and closes a fresh circuit of relay MD to prevent release of the selector. The calling party may cause the operator's lamp to flash by moving his switchhook up and down. Absorbing an accidental impulse. If only one impulse is received by the A-digit switch, when relay CA falls back, the release magnet ZA operates over springs NP, NA. Delay in dialling. If no impulses are received by the A-digit switch within a given time, ground pulses from TL2 operate relays TPA, M. Relay K falls back and frees the A-digit switch, and lamp SL is lighted. Relay A remains held locally. If dialling now occurs, the first impulse is repeated by relays L, A to the vertical magnet V, and relay C then falls back and closes the stepping circuit for the rotary magnet ROT. The selector moves to the 11th position, in which NU tone is connected to the calling line. If delay occurs at a later stage, the loop to the succeeding switches is broken at the registercontroller and ground is connected to wiper TPW to operate relays TPA, M. Relays K, C fall back and the first code selector is stepped to the 11th rotary position as before.