Patent GB-618900-A (GB)
Title: Automatic telephone system
IPC: H04M15/38
Filed: 1946-10-01
Abstract: 618,900. Automatic exchange systems; metering. WESTERN ELECTRIC CO., Inc. Oct. 1, 1946, No. 29235. Convention date, May 22, 1940. [Class 40 (iv)] An automatic system includes means for ascertaining the line-finder terminal number of the calling line in accordance with the movement of a line-finder switch, and means for electrically translating the line-finder terminal number into an arbitrary directory number, a recorder circuit being arranged to record the directory number together with the charge assessed for the call. A pair of stepping switches register the number of vertical and rotary steps taken by the line-finder switch in locating the calling line, the stepping switches controlling a cross-bar switch which marks one of a set of terminals to identify the linefinder terminal number. The marked terminal is cross-connected to one of another set of terminals to identify the directory number. All calling lines entitled to a flat rate service are connected to upper terminal levels of the line-finders and those entitled to individual message rates to the lower levels, normal post springs 324 in each line-finder being adjusted to close at the upper levels. Operation of allotter and line-finder. When the subscriber at sub-station A lifts his receiver, a combined line and cut-off relay 111 energises partially to earth conductor 112 to mark the commutator segments of the corresponding level in the banks of the finders of both subgroups and also mark test terminal 119, and if there is an idle finder in the related sub-groups so that relay 457 is operated, circuit is made over conductor 220 to energize start relay 450, which causes the ringing interrupter 463 to operate and also energizes an alarm circuit 460 to effect alarm if relay 450 should be energized unduly long. Relay 450 also energizes relay 451 which establishes a circuit over brush 475 for operating the line relay 500 of the selector associated with the allotted line-finder. Relay 500 energizes a slow-release guard relay 501 which connects earth through the permanent signal timing circuit TC to energize relay 503 to earth conductor 300 to prepare for the finding of the calling line, during which operation relay 451 holds relay 457 operated in case this linefinder is the only idle finder in the group. Relay 451, through brush 474 of the allotter switch, operates stepping relay 452 which interacts with vertical magnet 343 to step the brushes of the line-finder up level by level until they reach the level of the terminals of the calling line when relay 452 is held operated over wipers 472 and 238 to prevent re-operation of the magnet 343. This results in the energization of the upper winding of relay 453 which locks over its lower winding to transfer the stepping circuit to the rotary magnet 344 to step the brushes of the line-finder horizontally until the upper or lower set 131-133 or 134-136 engages the terminals of the calling line, when relay 452 is held operated and upper or lower relay 341 or 342 operates to complete energization of line relay 111 and connects the calling line, via conductors 302, 303, to the line relay 500 of selector S. The energized relay 341 or 342 also operates relay 454 which releases relays 451 and 452. The release of 451 breaks the holding circuit to relay 457 which does not release, however, if there is another line-finder idle. The release of 451 also releases 453 to operate a self-interrupting stepping magnet 470 to advance the allotter switch to select the next idle line-finder, when relay 454 releases. The control circuit LFC-A is then ready to operate in response to another call. If all the linefinders in the sub-group are busy, relay 457 releases and transfers the connection on conductor 220 to conductor 220 of the line-finder control circuit LFC-B, Fig. 2. Operation of selector switches. Dial tone is transmitted to the caller in usual manner, and when the first digit is dialled, relay 500, Fig. 5, is alternately released and re-operated by each impulse in the train, to energize a change-over relay 509 and to operate a vertical magnet 506 to raise the brushes 511-514 of the selector. The first selector comprises a set of normal postsprings 529 adjusted to close at a predetermined level above which multiple charges are made for trunk outlets. When these springs close, the lower winding of relay 304 energizes for a purpose described later. Local calls. For all lower levels in the first selector, relay 304 does not energize and connection is made to a second selector S2 which is adapted in known manner to reverse the current upon the response of the called subscriber. This operates relay 305 through an interrupter circuit 325 to operate relay 306 and magnet 310 to advance the charging switch one step. After an interval, relay 305 releases to release the magnet 310. Upon release of the line, switching relay 502 falls back and initiates release of the selector S and line-finder LF1. Relay 455 operates and locks under control of the peg counter register 456 and connects earth to the alarm circuit 460 in case the line-finder fails to release. When the line-finder reaches normal position, V.O.N. springs 345 return to release magnet 349 and relay 455, which releases the register 456. Trunk calls. After the first train of impulses has been received, change-over relay 509 releases slowly to energize a rotary magnet 507, and in co-operation with relay 510 steps the brushes round until an idle repeater circuit R is found and switching relay 502 operates to disconnect conductors 302, 303 from relay 500 and connect them through brushes 511, 512 to the selected repeater, relays 500, 501 and 503 releasing. The line relay 551 operates relay 532 and responds to subsequent dialling trains of impulses and repeats them over trunk T to establish connection with the called station AS2. Testing and ringing ensue in known manner. Removal of the receiver at station AS2 operates the supervisory relay 553 in the repeater R in usual manner to reverse the current through the polarized supervisory relay 301 which operates 305 temporarily and 306 to extend the conductor 317 through polarized relay 307, slow-release relay 309 and magnet 310 of the charging switch 330. The line-finder circuit is now ready to receive impulses over conductor 317 indicating charges to be made, depending on the zone to which connection is made, or on the duration of the call, or both. Metering trunk calls. Operation of the supervisory relay 553 energizes relay 536 which locks up. Operation of the repeater now depends on whether the calling line is entitled to flat rate or individual message service. In the former case, as already described, normal post-springs 324 are closed and relay 542 is operated. In the latter case, relay 542 is not operated. Individual message service. With relay 542 not operated, operation of relay 536 energizes relay 543 which closes a circuit through brush 514 of selector S and conductor 317 to operate the magnet 310 and advance the brush 313 of the charging switch one step. Relay 536 also energizes relay 525 which then releases relay 543 and magnet 310. Energization in turn of slow-operating relays 538, 537, 540, 539 alternately operate and release magnet 310 to advance the charging switch 330 a further two steps. Flat rate service. With relay 542 operated, the circuit to relay 543 is not completed, and the number of pulses sent to the charging switch is one less. Over-time registering apparatus may be incorporated in the repeater R by placing battery at relay 539 and its Nos. 1 and 2 contacts under control of the timing apparatus, which releases 539 at the beginning of the overtime interval. If relay 552 is still operated at the end of the interval, when relay 539 is reenergized, the repeater operates to send an extra charging impulse to the switch 330. Identification of calling station. The identification circuit is common to three groups of finders. In parallel with the vertical magnet 343, Fig. 3, and the rotary magnet 344 respectively are magnets 532 and 533 of two rotary stepping switches 520, 530 which therefore move with the line-finder brushes and together constitute a two-co-ordinate line-finder for 100 lines. The terminals of these switches are connected respectively to ten select magnets 610-619 and ten hold magnets 660-669 of a cross-bar switch 650, Fig. 6. When charging is completed, relay 309 releases slowly to extend earth to conductor 318 to energize a relay 601 individual to the trunk, the relays 601, 602 providing non- interference if two or more trunks should call simultaneously for the recording circuit, since any relay 601 locks and energizes 602, which cuts out the lower windings of all other relays 601. For each group of trunks serving the same line-finder group, there is one relay 603 which provides, with a single relay 604, non-interference between line-finder groups. The operated relay 602 energizes relays 603, 604, and therefore relay 605, to mark the line-finder group associated with the calling trunk, there being other relays 606, 607 for other groups. If the calling line is in the lower terminal bank of the line-finder frame, relays 342 and 312 have energized, and now relay 605<SP>1</SP> (or 606<SP>1</SP>, 607<SP>1</SP> as the case may be) also operates. Operation of relay 605 establishes a circuit over the brush 521 of the switch 520 and one of the conductors 531 to one of the select magnets 610-619 in a cross-bar switch of the type described in U.S.A. Specification 2,021,329. The select magnet energizes a relay 621 which co-operates with the switch 530 to energize one of the hold magnets 660-669. Thus the select and hold magnets position a six-wire switch 613 according to the vertical and rotary positions of the linefinder, one pair of terminals is selected according to which of the relays 605, 606, 607 is energized, and the final distinction between lines in upper and lowe