Patent GB-254003-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1925-03-25
Abstract: 254,003. Standard Telephones & Cables, Ltd., (formerly Western Electric Co., Ltd.), and Baker, J. H. E. March 25, 1925. Automatic and semi-automatic exchange systems.-A system employing register-controllers of the code-translating type is provided with a first code selector which is adapted to be taken into use solely by an operator, and which has access over a hunting switch to an " A " digit switch in the usual manner. Means are provided for giving a busy signal if a busy condition is encountered at any stage, or if the ' A ' digit switch fails to find an idle outlet. If the operator dials before an ' A ' digit switch is seized, no further switches are taken into use, while if she omits to dial or dials an insufficient number of digits, the register-translating equipment is released. An engaged lamp is lighted when the selector is removed from the frame. Normal operation. When the operator plugs into jack J, sleeve relay SR energizes, lighting lamp EL and grounding the test and start wires RT, SW. Line relay L energizes over the circuit BF10, H15, K29, H28, KA6, and connects up impulse relay A at contact L5 and release relay* B at contact L7. The magnet of the ' A ' digit switch finder is now connected up over the circuit RM, H6, B6, K6, PD to the test wiper, while test relays K. KA are connected to an intermediate point, the other ends of their windings being grounded over the circuit BF5, A6, S5, B9, H26. Relays K, KA energize in the usual manner when an idle ' A ' digit switch is found. Relay K grounds the test wire PD, connects relay A to the outgoing impulse circuit L+, L- and substitutes wire PS and the impulse relay in the ' A ' digit switch for the left winding of line relay L. Relay KA locks to the test wire RT, and connects busy wire AB to relay BF. The operator dials upon receiving dialling tone, and the first train of translated impulses are received by relay A and repeated at contact A6 to the vertical magnet V and series relay C, which at the first impulse connects up stepping relay G. Relay G locks to the test wire, and when relay C falls back at the end of the train, the rotary magnet R operates over the circuit G5, C7, K25, B9, H26 and interacts with relay G, the energizing circuit of which is over contacts H35, H11 to the test wiper P, test relay H being short-circuited as long as grounded test terminals are encountered. When an idle outlet is found, relay H energizes in series with relay G, which is now inoperative, locks and switches through the talking and test wires in the usual manner. Impulse relay A relapses, while line relav L is held at contacts K32, H15 and relay K is held over the test wire PD. When all the impulses have been transmitted, relay K is released in the ' A ' digit switch and connects jack J to the line wipers. Relays L, B relapse, and only relays H, KA are energized during conversation. When the operator removes her plug. sleeve relay SR removes ground from the test wire RT and relays H, KA fall back, and release magnet Z restores the selector. A restoring circuit for the ' A ' digit switch finder is completed over wires RM, H. Busy signal and release. If the selector finds no idle outlet, cam springs S are closed in the 11th rotary position, so that busy relay BF energizes, disconnecting release relay B, replacing the left winding of line relay L and applying busy flash BF to the right winding. The remaining digits are sent, and relays K, A are then disconnected in the ' A ' digit switch, and release takes places as before when the operator's plug is removed. A statistical meter may be operated over the 11th test terminal. If a subsequent switch finds no idle outlet, busy flash is sent back therefrom, and release takes place in a similar way. ' A ' digit switch finds no idle outlet. In this case wire AB becomes grounded, and busy relay BF energizes, locks and sends busy flash until the plug is withdrawn. Premature dialling. Should the operator dial before an ' A ' digit switch has been seized, line relay L repeats impulses at contact L5 to impulse relay A. Relay G cannot energize since contact K25 is open, so that at the first vertical step, test relay H is not short-circuited and energizes as when an idle outlet is found, and releases relays L. A, B. The selector is held until the operator clears. Permanent loop. Should the operator omit to dial, or dial an insufficient number of digits, a timing device in the ' A ' digit switch momentarily grounds impulse wire PS, short-circuiting line relay L. Relays L, B fall back, and the 'A' digit switch is released for further use. Removal of selector from frame. Connections to the selector are made by means of jacks cooperating with springs on the frame. When the selector is removed from the frame, springs engage to ground the test wire RT, energizing a busy relay BR, which disconnects sleeve relay SR and lights lamp EL.