Patent GB-202968-A (GB)
Abstract: 202,968. Automatic Telephone Manufacturing Go., Ltd., (Assignees of Wicks, J.). Aug. 25, 1922, [Convention date]. Semi-automatic exchange systems.-A tolloperator's cord circuit O, Fig. 1, for extending connections received over a toll trunk Y, Fig. 2, is provided with a marginal sleeve relay 36 the energization or non-energization of which so controls the cord circuit that when, at the end of a conversation, alternating current is projected over the trunk Y by the originating operator, this current, in the case of a call which has been extended over a further toll line X, Fig. 1, passes straight through the cord to signal the distant operator, but, in the case of a call completed over automatic switches F, G, H, M, Figs. 3 and 5, is prevented by the opening of the lower talking conductor from passing on and so re-ringing the called subscriber A. The relay 36 also controls a bridge across the cord so that, for calls completed over the switches F - - M, a supervisory relay 35 is connected up to control the called supervisory lamp L<3>. The toll trunk Y terminates at each end in a repeater R and selector E leading to other toll lines, and is accessible over terminals 244, 245, 246 to other toll lines leading out at their other ends from similar repeaters R and selectors E. An operator at the distant end of the trunk Y may either extend a connection through the cord O, in which case the operator, Fig. 1, is called by ringing current, or, after seizing the trunk, may dial a digit to operate the selector E, in which case the cut-off relay 2 is operated to disconnect the call-up relay 3 and to mark the trunk Y busy at indicator 8. Calls may be extended in a similar manner from cord circuit 0 over the trunk Y, either to signal the distant operator, or by dialling a digit to control a selector similar to selector E at the distant end of the trunk and so extend the connection to a further exchange. In the latter case, the movement of dialling key K<1> to the left, throws a resistance 38 into the sleeve circuit, and the resulting relapse of a marginal relay 257, Fig. 2, causes a relay 259 to connect up the line relay 256 which, at its armature 220, repeats impulses from dial CD over a simplex circuit, including the two conductors of trunk Y in parallel. When key K<1> is restored, relay 259 remains locked up and line relay 156 remains energized over a local circuit independently of the sleeve circuit, this arrangement eliminating the necessity of providing a special holding bridge across the talking conductors of the cord. The circuit arrangements at connector M, Fig. 5, are such that, when the wanted line A is reached, the seizure of the line to mark it busy and the ringing of the called subscriber do not take place automatically, but are each dependent on separate operations of the operator. In the system described, the line is marked busy by a first transmission of ringing current, and the wanted subscriber is called by a further separate transmission of ringing current. The operator may thus control the switch to select the line A at any convenient moment, but need not seize the line or ring the subscriber until informed that the originating subscriber is also ready. If line A is at this moment idle, lamp L<3> will be flashed intermittently, but if during the waiting period, the line has become engaged in a local call, lamp L<3> remains extinguished until the line again becomes idle, when the flashing is resumed.. In a modined system, the selector E, Fig. 2, may have several levels multipled to corresponding levels of local selectors and only one level extending to toll-switching selectors. In this case, the operator at the distant end of the trunk Y may complete a connection to a local subscriber A without employing the operator, Fig. 1. Call to subscriber A incoming over toll trunk Y and completed over automatic switches F, G, H, M; cord-circuit O. When the distant toll operator seizes trunk Y, battery placed upon the two conductors in parallel energizes relay 261 at repeater R, relay 262 also responding to ground conductor 26. Ringing current transmitted over the trunk Y energizes relay 3, Fig. 1, which lights lamp L' and operates busy indicator 8. The insertion of plug P in jack J<1> energizes relays 30, 257, 258 in the sleeve circuit. Relay 258 disconnects relays 261, 262 which relapse, but conductor 26 remains grounded at armature 227 to mark the trunk Y busy at test terminal 245. Relays 257, 258 close the circuit for the lower winding of relay 259 which is adjusted so that only contact 229 is operated at this time, to connect up the upper winding which, however, is short-circuited at contacts 226, 222, 230, 227. Relay 258 also grounds conductor 28 to operate relay 2 which cuts out lamp L' but maintains indicator 8 operated. Relay 30 closes a circuit for relay 31 which does not energize, being short-circuited over contacts 39, 41, 45. The local operator throws her key K<2> to the left to connect up her headset and on learning that a subscriber A, reached over automatic switches, is required, inserts plug P' into the jack J<2> of an idle trunk TC<2>. Relay 54, Fig. 3, energizes in series with marginal relays 36, 55, neither of which energize, and conductor 50 is grounded to operate busy indicator 46. The operator restores key K<2> and throws dialling key K<1> to the right, a direct ground connection at the lower springs causing relay 55 to energize, lock up, and close the lower talking conductor at con. tact 61. Selectors F, G. Line relay 65 of selector F energizes over conductors 51, 52, leads 13, 14 and impulse springs 15 of operator's dial CD. The selectors F, G operate in known manner in response to the first two digits to extend the connection to an idle selector H, Fig. 4. Selector H. When trunk 97, 98, 99 is seized, line relay 110 energizes over its upper winding, normal contacts of armatures 150, 123, 117 in series with impulse springs 15 to ground at the normal contacts of armature 120. The next set of impulses is repeated by relay 110 to vertical magnet 152 in series with relay 112, which energizes stepping relay 113 to prepare a circuit for rotary magnet 153, and at the end of the impulses, the wipers 156 - - 159 hunt in the usual manner until an idle connector M, Fig. 5, is found when switching relay 109 energizes to close contacts 130, 134 and to ground leads 161, 162. The of off-normal contacts 147 upon the first vertical step completes a circuit for the lower, winding of relay 105 which, however, does not energize owing to the high resistance 115. The closure of contacts 130, 134 connects the upper winding of relay 105 in series with line relay 165 of the connector, but relay 105 still does not energize since the currents in its two windings are in opposite directions. Connector M. Relay 165 energizes in series with the upper winding of relay 105 and completes the circuit 191, 208, 176 for release relay 166 which prepares the circuit for the vertical magnet and also energizes ring-cut-off relay 168 which locks itself to grounded lead 161 and connects conductors 160, 163 to armatures 206, 285 respectively. The tens and units impulses are repeated by relay 110 at armature 135 to relay 165 to operate the vertical and rotary magnets 186<1>, 187 respectively in the usual manner. Wanted line busy, subsequently becoming idle. Rotary series relay 173 connects busy relay 172 to the test wiper 212, and if the wanted line is busy, relay 172 energizes, and as soon as relay 173 releases, locks itself over contacts 199, 197 to the test wiper. Relay 169 energizes in this locking circuit and (1) locks itself to lead 161; (2) bridges contacts 199, 197 in the locking circuit of relay 172 at contacts 199<1>, 189 respectively; (3) energizes relay 171 which locks to lead 162; and (4) breaks the circuit of release relay 166 which deenergizes. Relay 171 transfers the locking circuit of relay 168 to its grounded contact 193. Relay 172 also connects up busy tone to the lower talking conductor at contact 200, and upon hearing this, the operator may restore her key K<1> and wait for the line to become idle. The restoration of key K<1> bridges polarized relay 35 across the cord in series with armature 44. When line A becomes idle, the release of busy relay 172 energizes relay 174 over the circuit 196, 187<1>, 162. Relay 174, at contacts 285, 206 reverses the connections between leads 160, 163 and the windings of relay 165 which reversal causes polarized relay 105 to energize and lock up over contact 116 independently of its upper winding. Relay 105 reverses the connections from relay 110 to conductors 97, 99 causing polarized relay 35 to light lamp L<3>. Relay 105 also bridges relay 107 in series with condenser 164 across conductors 97, 99 and connects relav 106 to conductors 160, 163 in series with relay 165. Relays 106, 165 do not energize, their battery and ground connections being similar. Interrupter I, connected up by relay 174, intermittently grounds the lower talking conductor, and at each grounding relays 106, 165 energize, the former opening the circuit between relav 110 and leads 97, 99, relay 110 however remaining energized over a local circuit 123, 139. The disconnection of leads 97, 99 de-energizes relay 35 and extinguishes lamp L<3>. When ground is removed from conductor 163, relay 35 re-energizes and lamp L' is lit, the flashing of the lamp before the operator indicating that the wanted line has become idle. Should the operator neglect to seize the line, it may become busy again in a local connection, in which case relay 172 energizes over contacts 199<1>, 189, 212 to disconnect interrupter I and connect up busy tone over contacts 205, 200. Relay 106 remains energized over contacts 200, 205 so that lamp L<3> remains extinguished to indicate to the operator that the line has again become busy, a confirmatory busy tone