Patent GB-246550-A (GB)
Title: Improvements in or relating to automatic and semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1924-10-23
Abstract: 246,550. Automatic Telephone Manufacturing Co., Ltd., (Automatic Electric Co.). Oct. 23, 1924. Automatic and semi-automatic exchange systems; metering; party-line systems.-Relates to systems in which talking battery is fed to the called party from the first local numerical switch and in which battery and earth are fed forward over the two speaking leads during impulse transmission. The invention comprises the following principal features. (1) All the numerical switches in an exchange other than the first switch taken into use are provided with line relays normally connected across the speaking leads and having no battery or earth connections. (2) The dialling current fed forward in the direction of the called party is first fed through two back-bridge relays which give supervisory signals on the cessation of the setting operation and bring about metering or supervision when the called party replies. (3) When some exchanges of a network are of the kind in which talking current is fed to the called party from the first local switch, whilst others are of the kind in which feed current is supplied from the connector, the line relays of incoming selectors of exchanges of the latter type are bridged directly across the speaking leads. (4) At incoming selector repeaters of exchanges of the latter type, an impulsing loop is connected across the outgoing speaking leads, there being no battery or earth connections at this switch to either the line relay across the incoming leads or to the impulsing loop across the outgoing leads. Other features of the system described in detail below are claimed in Specification 246,775. The system described comprises a mixed network of exchanges in which some of the exchanges are of the kind in which for local calls battery is fed to the called party from the first selectors, whilst others are of the usual kind in which for local calls the battery feed to both parties is from the connector. In an inter-exchange connection from an exchange of the first selector feed type to another exchange of the same kind the back bridge relays at the first selector repeater relapse and prepare the metering and other supervisory circuits when the setting operation has been completed, and subsequently re-energize to bring about metering and supervision when the called party replies. Talking current is supplied to the calling party from the first selector repeater and to the called party from the incoming selector repeaters. If the connection is from a first selector feed exchange to an exchange of the connector feed kind, the completion of the setting operation produces no change, but the back bridge relays at the first selector repeater relapse and prepare supervision when the wanted party replies, and then re-energize and complete supervision a moment later on the relapse of a slow release relay in the connector. In this case talking current is fed to the calling party from the first selector repeater and to the called party from the connector. Slightly modified forms of first selector repeater circuits are described for use in (1) systems using register-controllers of the code-translating type, and (2) networks in which all the exchanges are of the first selector feed kind. In each case the first selector repeater may be used for extending revertive calls in party-line working to a revertivecall ringing switch, when a special number is dialled. The supervisory back-bridge relays are also operated to control the circuits of exchange attendants' supervisory lamps and to change the release control when the connection is extended to a manual operator's position. Call between two first selector feed exchanges in a mixed network : first selector repeater, Fig. 1. A calling subscriber A, Fig. 1, is extended to a wanted party B, Fig. 4, in a distant exchange, over a line switch LS and first selector repeater, Fig. 1, an incoming selector repeater, Fig. 2, an intermediate selector. Fig. 3, and a connector, Fig. 4. The calling line is extended to an idle first selector repeater by the line switch LS in known manner. The line relay 32 energizes release relay 33 and closes a series circuit 58, 54, 57 for relays 40, 39. Relay 33 closes a circuit over the bottom low-resistance winding of a marginal relay 31 for relay 34, which connects the dial tone conductor 25 to the upper talking condenser. The calling party now dials the first digit of the wanted number and the relapses of the line relay 32 energize the vertical magnet 48 and the parallel change-over relay 37, which energizes the stepping relay 38. The movement of the off-normal spring 44 bridges the upper talking condenser across the line to cause the line relay to respond more readily to the impulses. At the, end of the vertical movement, the relapse of the relay 37 closes the circuit of the rotary magnet 49, after which the stepping relay 38 and the rotary magnet 49 interact in the usual manner until an idle trunk 92 - - 94 is engaged, when the switching relay 41 responds and bridges the relays 39, 40 across the outgoing trunk in series with both windings of the line relay 107 in the incoming selector repeater, Fig. 2. If all the trunks are busy, on the closure of the eleventh step contacts 47, the busy lead 23 is connected to the lower conductor. The circuit of the switching relay 41 is opened at contacts 46 to prevent the possibility of false operation of the meter. Incoming selector repeater, Fig. 2. Relay 107 closes a circuit over resistance 117 for repeating relay 102, which energizes release relay 103, and closes a series circuit over the upper windings of relays 109, 105, 106, all of which respond. Relay 109 locks over its lower winding, connects the upper winding of relay 107 directly across the line, and shunts the upper talking condenser across it to improve the impulsing circuit, shortcircuits the resistance 117 to provide more current for the relav 102, earths the right-hand side of the lower talking condenser, and connects the left-hand side through a resistance 119 to the repeating armature 134 of line relay 107 to improve the response of repeating relay 102. When the calling party dials the second digit, at each relapse of the line relay 32 the battery bridge across the outgoing trunk is opened at armature 58. In the first selector repeater, Fig. 1, the relays 39, 40 de-energize, but the relay 34 is energized during the impulse series, maintains open the circuit of relay 35, and short-circuits relay 39 and shunts the upper talking condenser across the calling line to improve the impulsing circuits. In the incoming selector repeater, Fig. 2, the impulses are transferred by relay 107 to relay 102, upon the first relapse of which the relays 105, 106 de-energize, but the holding circuit of relay 109 is transferred to the control of the change-over relay 104. The relapses of the relay 102 energize the vertical magnet 120 : at the first step the stepping relay 108 . locks energized rom earth at armature 141 and prepares the circuit of the rotary magnet 118. At the end of the impulse series, the relays 105, 106, 109 restore to their previous condition and the relapse of relay 104 completes the circuit of the rotary magnet 118. The relay 108 and the rotary magnet 118 now interact in the usual manner until an idle trunk 161 - - 163 is engaged, when the switching relay 110 energizes, connects the relays 105, 106 to the trunk conductors 161, 163 in series with the bridged line relay 201 of the intermediate selector, Fig. 3, and connects earth from armature 141 to the lower trunk conductor 163. Eleventh step contacts are provided for connecting up the busy tone lead 175 if all trunks are engaged. Intermediate selector, Fig. 3. Line relay 201 closes a circuit over release trunk 162 and resistance 202 for a combined release and change-over relay 203. The next impulse series is repeated at armature 123, Fig. 2, of the line relay 102 of the incoming selector repeater, to the line relay 201, which repeats them to the vertical magnet 209. Springs 212 close at the first step, energizing the stepping relay 204 which locks to earth at armature 231 and prepares the circuit of the rotary magnet 210. At each subsequent energization of the line relay 201, the relay 203 is shortcircuited over vertical off-normal springs 214. The relay 203 is thereby rendered slow-to-release and holds during impulsing, but on the cessation of the impulses it falls away and completes the circuit of the rotary magnet 210. Thereafter the relay 204 and the rotary magnet 210 interact until an idle trunk 236 - - 238 is found, when the switching relay 205 energizes and extends the trunk conductors 161 - - 163 to the connector, Fig. 4. Eleventh step busy-tone contacts 213 are provided as in the previous switch. Connector, Fig. 4. The combined change-over and ring cut-off relay 303 energizes over the earthed release wire 237 and prepares the circuit of the vertical magnet 312, and the bridged line relay 301 energizes in series with the upper windings of relay 105, 106, Fig. 2, at the incoming selector repeater and energizes the release relay 302, which locks to the release wire 237 over armatures 324. 332, 341, 323. When the calling party dials the fourth digit, at each relapse of the line relay 301, the vertical magnet 312 and parallel relay 305 are energized. Relay 305 holds up the relay 303 after the opening of the offnormal springs 310 until the end of the impulses, when both relays 305, 303 relapse and the latter relay transfers the operating circuit to the rotary magnet 311, which on the receipt of the last digit rotates the wipers to the wanted line. During these impulses the relay 305 is energized to connect the test wiper 344 to the busy relay 304, and to shunt the armature 332 and so prevent release if the test wiper passes over a busy test contact. Busy test, signal, and release. If the wanted line is engaged, the