Patent GB-199000-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1923-04-20
Abstract: 199,000. Western Electric Co., Ltd., (Assignees of Williams, S. B.). June 6, 1922, [Convention date]. Automatic exchange systems.-In a system in which subscribers' lines arranged in " vertical " groups 100, 104, 110; 106, 107, 111; 112, 113, 114, are connected to outgoing trunks 202 over crossbar switching mechanism, the arrangement is such that, in the event of simultaneous calls occurring on lines in various groups, a second call in any particular group is only extended after a first call in every other calling group has been dealt with. The switching mechanism, Fig. 2, is of the type described in Specification 183,438, and comprises intermediate link circuits 206, 217. Fig. 3 shows the arrangements for control. ling the order of extending calls, each set of three relays enclosed in dotted lines being common to a particular group, whilst the remaining apparatus is common to the whole system and includes a step-by-step switch D which preselects the next idle trunk 202. In extending simultaneous calls, preference to " vertical " groups is given from left to right, and to the members of a group from bottom to top. For example, line 100 is extended before line 106, and line 106 before line 107. Single call in one group. When a subscriber 100 removes his receiver, his line relay 101 completes a circuit 302, 102 for group relay 300 which energizes common relay 304 and group relay 303. Relay 303 energizes relay 301 and locks up in series with relay 305 which, in turn, energizes slow-release relay 308. Relays 303, 305 complete a circuit for vertical magnet 200 associated with the calling vertical group A, which magnet rocks its shaft and also energizes relay 204 which locks up in series with relay 313. At the same time, the vertical magnet 201 associated with the next idle outgoing trunk 202 is energized over wiper 309 of preselecting switch D. Magnet 201 (1) rocks its shaft, (2) locks up in series with relay 306, (3) energizes a relay 203 individual to the trunk 202, and (4) effects the completion of a circuit over wiper 312 for stepping magnet 311 which steps forward wipers 309, 312 of switch D to preselect the next idle trunk. Relays 306, 313, 204 energize the horizontal magnet 205 associated with the first idle link 206, and members 208, 209, operated bv the combined action of magnets 200, 201, 205 connect the calling line through the link 206 to the trunk 202. Supervisory relay 210 energizes in series with the calling loop and completes the circuit of relay 212 which locks up magnet 205 in series with relay 207, and energizes the cut-off relay 103. The latter operation de-energizes relays 304, 301 whilst the energization of relay 207 preselects the next idle link-circuit 217. Relay 306 also breaks the circuit of relay 308 which, after a short interval sufficient for the operation of magnets 200, 201, 205, falls back and unlocks relays 303, 305, thereby releasing the magnets 200, 201 and restoring the relay set Fig. 3, to normal, the connection being maintained by magnet 205 alone. When the calling subscriber hangs up, the de-energization of supervisory relav 210 causes the release of relays 103, 212, 203, 207 and magnet 205. Two simultaneous calls in the same group. If lines 100, 104 call simultaneously, line 100 has preference since the energization of relay 204 prevents the energization of the horizontal magnet 214. The call on line 100 is extended as described in the preceding paragraph, but upon the energization of the cut-off relav 103, relay 304 remains energized over a front contact of line relay 105 and maintains relay 301 locked up. When relays 305, 306 de-energize, slow-release relay 307 energizes, unlocks relay 301 and deenergizes relay 304. Since line relay 105 is still energized, a new circuit for relay 300 is completed and the extension of the call on line 104 proceeds in the manner previously described for line 100. Two simultaneous calls in different groups. If lines 100, 106 call simultaneously, relays 300, 303, 315 energize but relay 316 is prevented from energizing, at first by relay 300. and afterwards by relay 305. The call on line 100 is thus first dealt with, and when, after this has been extended, relay 305 de-energizes as previously described, relay 316 is able to energize and the call on line 106 proceeds in a similar manner. Two calls in the same group simultaneous with calls in other groups. If simultaneous calls occur on lines 100, 104, 106, 112, the call on line 100 will be given preference in accordance with the principles set out in the preceding paragraphs, and when, after this call has been extended, relays 304, 301 remain energized, relay 307 is prevented from energizing to release them by the operation of relays 315, 317. Relay 300 is thus prevented from operating again in connection with the call on line 104 in the same group, and line 106 is the next to be extended. When this connection has been completed, relays 304, 301, 319 remain operated, relay 307 is prevented from operating by relay 317 and the call on line 112 has next preference. When one call in each of the groups has thus been extended, relay 307 energizes to release relays 301, 319, 320, 304 and the second call in the first group is then dealt with.