Patent GB-233792-A (GB)
Title: Improvements in or relating to semi-automatic telephone systems
IPC: H04Q3/42
Filed: 1924-02-15
Abstract: 233,792. Automatic Telephone Manufacturing Co., Ltd., and Ostline, J. E. Feb. 15, 1924. Semi-automatic exchange systems.-In a system in which trunk calls are set up by B-operators by means of cord circuits, an operator's head-set is automatically connected in turn to calling lines under control of marking switches which provide for waiting calls, and upon plugging into the wanted line the cord circuit, is connected over a finder switch with the calling line. This arrangement may be employed either in place of call indicator equipment or as a reserve set for use in an emergency. The invention is described with reference to the call indicator system described in Specification 229,371, in which numbers are transmitted by means of code impulses. The call indicator is cut out by means of key 293, Fig. 3, which energizes relay 195, Fig. 2, to disconnect the trunk relay sets from the decoder and connect them to the operator's head-set by way of special marking switches, Fig. 4. Specifications 163,807 and 233,007 are referred to. Connection to an idle trunk, and operation of coder, Fig. 1. At the repeater R, relays 4, 7 energize, and connect up the line relay 13 of the normal-type switch CS which hunts for an idle coder in the usual way. Switching relay 16 connects up relay 45 which reverses the current in the calling loop in order to operate a polarized relay in the register-translator to initiate the sending of the remaining impulse trains. The next digit is repeated at contact 6 to the selector D which then selects an idle trunk 119, 120. Dead earth is removed from test wire 26 at the selector D and relay 25, which was previously short-circuited, energizes over its upper winding, locks, and at contacts 30, 31 connects the impulse circuit to the coder over wire 56, relay 68 and stepping magnet 76 of the switch DS. Further digits are stored in relay sets and an extra digit enerated in the register-translator for adjusting the resistance of the impulse circuit is recorded in relays 100, 101, as described in Specification 229,371. Relay 83 energizes when the last digit. has been recorded, and connects up over wires 57, 58 and the selected trunk line relay 121 of the switch SS, which operates in the usual way to select an idle trunk relay set, to which the trunk is connected upon energization of switching relay 125, which also operates a statistical meter. Extension of call to operator's head-set; distribution of calls, Figs. 2, 3, 4. Incoming calls are distributed among the operator's positions as in Specification 229,371, ground being disconnected in turn from the common test wires as 167 of the trunk relay sets leading to a single operator's position by relays such as 354 wired to terminals of a common distributing switch 360, 361, which, when a relay set is taken into use, advances a step to route the next call to the next operator. An operator's position is marked busy under various circumstances by the grounding of wire 210. Line relay 148 energizes and connects up its relief relay 160 and release relay 165. Relay 160 removes ground over wire 208 to render the relav set selectable at wiper 372 or 399, and, provided there are no waiting calls at the position, connects up relay 362 over wire 209 to initiate hunting of the marking switch 372, 373 to find the relav set which has been taken into use. Switching relay 365 upon energization connects up relay 168 over wire 208, transfers the start circuit 209 to the second marking switch 398, 399, and closes a circuit over wires 205, 207 for relay 153, which locks and connects the speaking leads over wires 203, 206 to the operator's head-set in circuit 308, 309. Relay 178 also energizes and locks in series with relay 374 over wire 204. The change-over of contacts 153, 159 releases relay 83 in the coder, which connects up the switch CSC to send out code impulses. As the call indicator has been cut out, these are effective only in energizing relay 385 to prevent objectionable noises in the operator's head-set. When all the impulses have been sent, relay 61 energizes, actuating a meter and releasing the coder. Relay 32 operates over wire 56 and switches through the speaking leads. Completion of connection by operator. The operator asks for the wanted number and sets up the connection with any idle plug. If the line is idle, sleeve relay 282 energizes, lighting lamp 287 and connecting up relay 252 which initiates hunting of the switch FS to find the calling trunk, which is marked by the removal of ground from test terminals 192 by relay 178. Switching relav 255 upon energization connects forward the speaking leads and energizes over the test wire relay 185, which locks, disconnects the operator's head-set, and releases relays 178, 374, so that, twostep relay 379 energizes fully, releases the first marker 372, 373 and transfers the control circuits to the second marker 398, 399. If a call has already been set up on the second marker, it is at once connected to the operator's head-set. As there are only two markers, the functions of a marker distributor are performed by contacts 368, 394 of switching relays 365, 391. Ringing. Line relay 247 energizes and connects up its relief relay 266, which extinguishes lamp 287, completes the ringing circuit and energizes relays 270, 274. Ring-cut-off relay 277 and back-bridge relay 249 and its relief relay 261 operate in the usual way, energizing relay 42, Fig. 1, by the reversal of current, so that relay 45 releases and current is reversed back over the calling loop to effect supervision or metering. Release is under control of the calling subscriber, and takes place as in Specification 214,195. Recall arrangements. If the called subscriber makes a call before the plug has been taken down, a visual and audible recall signal is given as in Specification 214,195. A similar action takes place if the calling subscriber hangs up before the called subscriber replies. Called line busy. If the wanted line is busy, upon plugging in a circuit is closed over the sleeve. relay like 282 of the other cord circuit in connection with the line, tip of plug 288 and induction coil 307, producing a click in the operator's head-set. She presses key 318 to connect busy tone to the lower speaking lead in the trunk relay set Relay 40 and busy relay 37, Fig. 1, operate and connect ground intermittently to the lower speaking lead to operate a flash signal. If the selec.tor D is driven to the 11th contact owing to all trunks in the level being busy, the action is substantially the same. In this case relay 25 is energized by battery through a, busy meter. Special service calls. These are trunked to a special operator by means of key 320 over a special service, finder SSF as in Specification 229,371. Prevention of release if the calling subscriber hangs up before the connection is completed. In this case, when relay 153 falls back, relay 23 is maintained energized over the lower speaking lead and contact 183 of relay 173. and prevents release of the repeater R.