Patent GB-290998-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1928-01-09
Abstract: 290,998. Associated Telephone & Telegraph Co., (Assignees of Stehlik, R. F.) May 23, 1927, [Convention date]. Automatic exchange systems. - In a system employing call finders, a group of call finders and the group of lines to which they have access are each divided into two sub-groups, the sub-groups of lines being first choices in the banks of the respective sub-groups of finders. The finders are two-directional and are set as regards vertical movements by impulses under the control of counting switches and as regards rotary movements by hunting operations. The system shown comprises a finder F of one sub-group having two sets of wipers and having access to two groups of 100 lines. Finder F normally deals with calls from lines of the first sub-groups of the two groups terminating in the first five levels, is preselected by allotter FA1 and is set by relay group CE1 under the control of counting switch VS1. If, however, all the finders in this sub-group are busy or the relay group temporarily engaged, the call is dealt with by one of a second sub-group of finders (not shown) in which the first sub-groups of lines appear in the last five levels, this finder being preselected bv allotter FA2 and set by relay group CE2 under the control of VS2. Busy relays in CE1 and CE2 which in normal use transfer the handling of a call from one sub-group equipment to the other, may be energized by an operator to put a faulty equipment out of service. If the vertical or rotary magnet fails, owing to dirty contacts, to operate fully at the normal rate of impulsing, provision is made for impulsing to take place at a slower speed; if the finder fails to take a vertical step it is switched over and rotated on its normal level to eleventh contacts and released. A group selector associated with the finder is prepared for operation before the finder is set. Marking arrangements. Counting switch VS1 is normally controlled by level marking relays 201 - - 205 corresponding to calling lines appearing in the first five levels of the first sub-group of finders. These relays ground the starting wire 277 of CE1 and mark the call in the second banks VS1 and VS2, the first six terminals in VS1 being connected to the last six in VS2. Counting switch VS2 is normally controlled by marking relays 206 - - 210 corresponding to lines appearing in the first five levels in the second sub-group of finders. These relays ground the starting wire 371 of CE2 and mark the call in the first banks of VS2 and VS1 the first six terminals in VS2 being connected to the last six in VS1. Setting of finder F of first sub-group. Call from subscriber A numbered 215 in the first sub-groups of lines energizes marking relay 201. Ground on starting wire 277 operates starting relay 308 of CE1 over conductors 374, 376 and contacts of relays 309 of CE1 and 401 of CE2. At 353, relay 308 closes the circuit of slow acting relay 301, both relays lock up to ground at 328 and the circuit of magnet 310 of allotter FA7 is opened at 334. Relay 301 extends ground from 327 over circuit (330, 333, 339. 274) to magnet 211 of VS1 and over in parallel circuit (330, 393, 272, 221, 225, 378, 394, 322, 72) to vertical magnet 9 of F. The vertical magnet raises the wipers to the first level and closes the revertive impulse. circuit over 77 to energize relay 303 which opens the circuit of magnets 211 and 9 at 333 and 331 respectively. Relapse of 211 advances VS1 and relapse of 9 opens the circuit of 303. If the call is not from a line in the first level, vertical magnet 9 again energizes in a circuit, as traced above but from wipers 221 to 225 over 261, 231, 260, F and VS1 being stepped on until wiper 221 encounters a terminal whose connection to 260 is broken by one of the marking relays. In the present instance, the circuit of magnet 9 is broken at 231 and ground from 327 on wiper 221 is extended over 265, 380. 395 to the upper windings of change over relay 304 and relay 303. Relay 304 locks up, opens its initial circuit at 338 and at 339, opens the circuit of magnet 211 and closes a point in the circuit of rotary magnet 10 of F. This relay also completes at 340 a homing circuit for magnet 211 over wiper 223. When 304 breaks its initial circuit, 303 restores and completes the circuit of rotary magnet 10. Interaction between 303 and 10 continues until calling line is reached when battery potential over cut off relay 1 on test terminal 76<1> energizes, switching relay 5 (upper), relay 302 (lower) and relay 303 (lower) in series over 71, 386. Switching relay 6 corresponding to wipers 50-52 is not operated and its connection to test wiper 51 is broken at 31. Relays 1 and 5 are held by ground returned over release wire 68 of the associated group selector S which was prepared for operation by.extension of ground from 325 over 67 to the upper winding of line relay 7 when CE1 was taken into use. The setting of finder F in response to a call appearing in levels 6 to 10 will be understood from the setting of a finder of the second sub-group described later. Operation of allotter FA1 and release of CE1. Relay 302, on operation'as described in the preceding paragraph, locks up and at 328 closes circuit of allotter magnet 310 and of relay 307 (upper). Busy finders return ground direct from 45 or over the release wire 68 to operate magnet 310. Relay 307 opens the circuit of 301 which releases after an interval followed by relays 308, 302, 304, relay 307 remaining energized over ground on wiper 222 of VS1 until VS1 returns to normal, and over ground on wiper 75 until an idle finder is seized to prevent relays 308 or 309 starting a call in CE1. As will be described later in connection with the corresponding relay 401 of CE2, relay 309 operates instead of relay 308 to start a call transferred to CE1 from CE2. All finders of first sub-group busy. Conductor 70 loses ground at the associated group selectors and short circuit over busy relay 306 (upper) is removed. Relay 306 closes circuit of relay 307 at 346 to change the starting circuit over to CE2. Setting of finder of second sub-group. The relays of group CE2 have functions similar to those of CE1 taken in reverse order, and their normal operation in conjunction with counting switch VS2 for a call appearing in the first five levels of the finders is similar to that of CE1 and VS1. The setting of a finder in the second sub-group will now be described in respect of a call from the first sub-groups of lines which appear in levels 6 to 10 in this finder, for example a call from subscriber A, all the finders of the first sub-group being busy. Relay 307 of CE1 operated as previously described extends ground on starting wire 277 over 375 to auxiliary start relay 401 of CE2 if idle. (If CE2 is busy, circuit of 401 will be broken by start relay 402.) Relay 401 energizes 409 and changes over the circuits of CE2 so that marking relays 201 - - 205 control the sending of vertical impulses to the finder through the last five terminals of the banks of VS2. The initial circuit of the vertical magnet of the finder extends from ground at 471 over 473, 382, wiper 225 of VS2, multipled terminals, 378, 474, and wiper 422 of allotter FA2. The vertical magnet and magnet 212 of VS2 receive impulses as previously described in connection with finder F and VS1, and at the sixth step VS2 brings its wiper 225 into contact with 261, the circuit, of the, vertical magnet being broken at 231 as the call is in the sixth level. Further operation of CE2 is similar to that described in connection with CE1. Defective circuits, arrangements for dealing with. The equipments CE1 and CE2 may be thrown out of service for repairs &c. by energization of busy relays 306, 404 by operators' keys 344, 454. If, due to dirty contacts, the finder magnets fail to return ground over 77 to energize relay 303 to terminate the impulses, slow pull-up relay 305 operates over 334, 330, and 327 to ground the wire 77 at 343 so as to operate the finder at a slower rate, if possible. If, however, the vertical magnet fails to step the finder, five ineffective impulses are sent to it, the counting switch VS1 reaches its sixth terminals, changeover relay 304 operates, and the finder is rotated on its normal level to the eleventh rotary position, whereupon springe 38 close to energize relay 302, which is followed by release of CE1 as before described. Release if call is abandoned during setting of finder. The finder will step up to the proper level if calling party is still on the line or to the fifth level if he is not, change over relay 304 will then operate with the results described in the last paragraph.