Patent GB-191001299-A (GB)
Title: Improvements in or relating to Telephone Systems.
Inventor: MARTIN TALBOT GRANT
IPC: H01H67/16
Filed: 1910-01-18
Granted: 1911-04-18
Abstract: 1299. Martin, T. G. Jan. 18. Automatic exchange systems.-For selective ring- ing on party lines the connectors are arranged in groups asscciated with ringing-generators supplying currents of different frequencies. The numbers of the subscribers on a given party-line differ only as regards the hundreds digit and the impulses representing this digit in a calling operation serve to select a connector of the appropriate group. Special means are provided for dealing with reverting calls between stations on the same partyline. The system described is of the sort in which the central-station instruments are energized by a grounded battery B', the subscriber earthing his vertical and rotary lines 199, 282 by buttons 393, 394 to control the various operations. The selectors K and connectors C<10> are of the general construction described in Specification 26,301/06, but the selectors are provided with additional relays 157, 177 required specially for reverting calls, and the connectors are modified to enable the sideswitch to move into its third position at an earlier. stage. The operations when subscriber No. 110 calls subscriber No. 410 on the same party-line are as follows. Selector. Subscriber No. 110 removes his receiver 385 from its hook 386 and grounds his vertical line 199 four times by the button 393, thereby energizing four times the vertical line relay 59 and vertical magnet 58 of his selector K, and raising the wipers to their fourth level so as to select a connector of the fourth group. The rotary line 282 is then grounded once by the button 394 to energize the rotary-line relay 107. The private magnet 138 is thus energized and de-energized and moves the side-switch into its second position, in which it connects in the rotary magnet 39 through the side-switch arm 197. The selector wipers 396, 397 are then moved in the usual automatic manner along the fourth level of the contact bank until the terminals of an idle connector C<10> are reached and the side-switch moves into its third position. Connector. The vertical line 199 is again grounded once for the tens digit (1) by the button 393, thereby energizing the vertical-line relay 200 and vertical magnet 207 of the connector, and raising the connector wipers 246, 247 to the first level. The rotary line 282 is then grounded once by the button 394, energizing the rotary-line relay 202 and the private magnet 216 of the connector, and moving the connector side-switch into the second position. Finally ten impulses, representing the units digit (0), are sent over the vertical line, and a single impulse over the rotary line. The ten impulses actuate the vertical line relay 200 and cause ten motions of the rotary magnet 213. The wipers 246, 247 are thus brought on to the tenth pair of terminals of the first level, these being the terminals of the line 199, 282. Busy test and busy release. If this line is already occupied by another connector, the release magnet 228 is energized as soon as the rotary line is grounded, the circuit being from the grounded test-wiper of the occupying connector, through the tenth contact of the first level of the connector test bank, through test wiper 249, side-switch arm 238, springs 220, 219 of private magnet 216, release magnet 228 and battery B' to ground G. The connector C<10> is thus released, and when the subscriber depresses his calling-button so as to ground the vertical line 199, the result is that the connector takes a vertical step, closing the normal contacts 260, 261 and connecting the busy signal coil 279 to line through the side-switch arm 239.. Special arrangements for reverting calls. If however the line 199, 282 is not occupied by another connector, it will nevertheless have been rendered busy by the first movement of the calling selector, which closes a circuit from ground G<8> through springs 186, 185 of a bridge cut-off relay 177, normal contacts 193, 191 (closed at the first movement of the selector), springs 176, 175 of a private normal relay 157, to the test trunk 378. It is obviously necessary that the guarding potential thus established shall be removed as long as the rotary line is grounded, for otherwise the connector would be restored automatically. For this purpose, when the rotary line 282 is grounded, the private normal relay 157 is energized and opens the above guarding-circuit, at the same time closing the circuit of the bridge cut-off relay 177 from battery B' through relay 177, springs 159, 175 of relay 157, test-trunk 378, connector test-wiper 249, and side-switch arm 238 to ground G'. In order that this circuit for the relay 177 may be completed, the connector is modified in such manner that the side-switch passes into its third position as soon as the private magnet 216 is energized for the second time. The relay 177, thus energized, opens the springs 179, 180, 181, so as to cut out the relay 157 and open the bridging-circuit normally established across the trunk lines 329, 330 by the vertical and rotary line relays 59, 107. The springs 186, 185 in the guarding- circuit are at the same time opened, and a selfholding circuit is closed from battery B' through relay 177, springs 184, 185, normal contacts 193, 191, springs 176, 175 of private-normal relay 157, test-trunk 378, connector test-wiper 249, sideswitch arm 238 to ground G<7>. The bridge cut-off relay 177 therefore remains energized until the instruments are finally restored, and serves, by opening the bridging-circuit of the relays 59, 107, to prevent the selector from being distributed by the ringing-currents which are sent back to the line 199, 282. Supply of ringing-current. The connector sideswitch being now in its third position, the circuits shown in heavy lines are completed through the arms 239, 240, and, when the calling-button is depressed so as to ground the vertical line 199, the ringing - relay 268 is energized, the circuit being from battery B<1>, through relay 268, sideswitch 237, springs 217, 218 of private magnet 216, springs 206, 205 of vertical-line relay 200, to ground G<6>, and the ringing-generator D is connected across the party-line 199, 282. The ringing- generator D is associated with all those connectors such as C<10> which have their terminals in the fourth .levels of the various selectors, and supplies current of such character as to affect only the rioging- apparatus of subscribers whose hundreds-digit is four. Thus, in the present instance, only the ringer 336 of subscriber No. 410 is affected. This subscriber now removes his receiver 362 from its hook so as to complete the talking-circuit between the two stations. Release. When the conversation is finished, either subscriber can restore the instruments by simultaneously grounding both sides of his line 199, 282. In the connector, the release magnet 228 is energized from battery B<1> through magnet 228 and springs 267, 266 of relays 263, 262, to ground. In the selector, the relays 59, 107 are both energized, the cut-off relay 177 having become de-energized when the connector side-switch arm 238 was restored, and the circuit of the release magnet 139 is completed from battery B<1> through magnet 139, springs of private magnet 138, and springs of vertical-line relay 59 to ground. Non-reverting calls. The operations when a subscriber on a different party-line is called are similar except that the selector relay 177 does not come into operation. In calls of this class the calling subscriber can complete the circuit of the connector release magnet 228 by simultaneously grounding both sides of his line so as to energize the relays 200, 202, and the private magnet 216.