Patent GB-654097-A (GB)
Title: Improvements in or relating to electrical communication systems
IPC: H04L12/54
Filed: 1948-02-27
Abstract: 654,097. Telegraph exchange systems; type-printing telegraphy. WESTERN ELECTRIC CO., Inc. Feb. 27, 1948, No. 6070. Convention date, Dec. 24, 1940. [Class 40 (iii)] A telegraphic interconnection system includes a number of switching centres or small exchanges, each of which, Fig. 3, provides interconnection between local subscribers A, B, one or more similar switching centres (over junction 226), a distant main exchange C, and a local operator R. Apparatus 372 ... 375 is also provided for transmitting the same message to a plurality of destinations anywhere in the system. In Fig. 3, the sets of equipment represented in six horizontal rows correspond to the different types of connection but calls to the operator R are received on teleprinters 311, 321, &c. associated with the separate incoming circuits. In the detailed circuit shown in Figs. 5-24, which should be arranged as shown in Fig. 4, the six horizontal rows of Figures correspond to the respective rows of Fig. 3. Fig. 2, included in Fig. 4 but not shown here separately, represents a second similar switching centre reached over junction 226. Interconnections are established over switching relays 728 &c. selectively operated by an operator under the control of indicating lamps and keys. Each set of equipment includes a printing reperforator 312 &c., Fig. 3, printing and perforating a tape 313 &c. in accordance with received signals, the tape controlling a transmitter 314 &c. which in turn controls the indicating lamps. For selecting purposes, each message is preceded by a single code-letter (A, B, C, &c.) and, according to the principal feature of the invention, the transmitters 314 &c. are so arranged that, after the sensing of this letter, the tape is stopped until the connection has been extended in accordance therewith, and the same code letter is then retransmitted in advance of the recorded message and is similarly repeated at other switching points until the desired destination is reached. The system also provides means for storing a message (on apparatus 372 ... 375) for a busy line and passing it on when the line becomes free, and for giving preferential treatment to urgent calls. Normal condition of system. When power is supplied to the system, the driving-motors of all motor-driven apparatus except 1669, 1690, Fig. 16, are energized for continuous rotation. Relays 547, 947, 1247, 1547, 1647 are operated to the right and magnets 548 &c. operated. Relays 592, 992, 1292 are also operated to the right and magnets 593 &c. operated. If tape 500 is not taut, contacts 682 operate relay 650 which energizes start magnet 672 to rotate the transmitting distributer until contacts 682 open. Similar operations take place for tapes 900, 1200, 1500, 1600, 1900, 2200. Relays 710, 720, 830 light lamps 761, 762, 863. Contacts 501 &c., 731 &c., are then closed as by keys, relays 562, 706 &c. are operated, and relays 710 &c. released, extinguishing lamps 761 &c. Relays 1665, 1687 are operated over normally-closed key 1556. Local call from subscriber A, Fig. 5, to subscriber B, Fig. 12; recording selecting code and message. If the circuits have not been fully conditioned for operation as described in the preceding paragraph, the substation initially transmits a " conditioning" code comprising " figures " followed immediately by " H." During each signal, slow-release relay 560 is operated. Relay 710 energizes to light busy lamp 761. On the "figures" code, contacts 538 are closed to operate relay 561 and, on the " H " code, relay 562 is operated over contacts 537. The station-selecting code-letter (B) followed by the message are then recorded on tape 500, the record consisting of partial perforations with superposed printing. The " B " code opens contacts 533 to release relay 562 which in falling back maintains relay 710 operated. A " letters " or space signal opens contacts 539 or 536 to release relay 561. At the end of the message, the conditioning code is again sent, causing relay 562 to re-operate. Relay 710 is released so that the calling line is free to receive a message from the central station. Selection of wanted line and transmission of message. The tape fed by reperforator 569 causes contacts 682 to close, operating relay 650 and magnet 672 as before. At each rotation of distributer 673, cam 674 through lever 699, plate 665 and bar 668 frees the selecting levers 664 to move into engagement with notched bars 667 carrying pins 663 which enter the holes in the tape. In response to the conditioning code, contacts 618, 617 respectively are closed, operating relays 707, 706. The station-selecting letter B operates contacts 613 energizing relay 702 which lights lamp 831 to indicate that a message from line A is waiting for line B. Relay 702 also operates magnet 671 to prevent the tape being fed forward at the end of the rotation of distributer 673, opens the circuit of magnet 672, and unlocks relay 706. If station B is idle (lamp 863 not lit), an operator throws key 837 to energize connecting relay 838 which completes a transmission circuit from distributer 673 over leads 645, 1268, relays 1292, 1247 and loop 1289 to station B. Relay 838 also operates, over lead 1259, relay 1265, which prevents magnet 1248 from responding to the signals and enables magnet 1293 of teleprinter 1290 to do so. Relay 839 energizes relay 830, to light lamp 863 and mark station B busy, and releases relay 702 so that distributer 673 recommences operation and the recorded message including the selecting code B is retransmitted in accordance with the successive settings of contacts 681. Breaking in. Operation of break key 1284 by subscriber B for the duration of two signal codes causes contacts 1295 in the monitoring apparatus 1290 to operate, lighting lamp 1296 and energizing relay 654 which stops distributer 673 and lights lamp 655. The operator may communicate with subscriber B by means of contacts 1294 and feed-back tape 500 for repetition of the message. The restoration of contacts 1295 and the momentary operation of key 656 to release relay 654 restores the circuits to the pre-break condition. Similar breaking- in facilities are provided in connection with other types of call. Tape feed-out. After the recording of the letter H at the end of a message, the printing reperforator 569 will stop advancing the tape and contacts 682 will open to stop the distributor. However, since relay 562 is operated by the letter H, relay 651 will operate on the release of relay 650. Relay 651 energizes slow-to-operate relay 652 and feed-out magnet 549. Magnet 549 causes the transmission of a series of all-mark codes and the advance of the tape whereupon contacts 682 reclose and the retransmission of the recorded message is resumed. After a time sufficient for this to be completed, relay 652 pulls up its armature and lights lamp 872. The operator throws key 874 to operate relay 653 which releases relays 651, 652 and magnet 549. The mechanical operations controlled by magnet 549 are described in a later paragraph. Release. When the conditioning code at the end of the message is received in the transmitter of Fig. 6, contacts 618, 617 are successively closed operating relays 707, 706 to unlock relay 838. In the monitoring apparatus 1290, Fig. 12, contacts 1291 are momentarily opened by the reception of this code to release relay 1265. Call from subscriber A, Fig. 5, to central station. If subscriber A transmits a second message, for the central-station operator, immediately following the message for station B, the selecting code-letter R causes the closure of contacts 540 to operate relay 565 which removes positive battery from the upper terminal of magnet 593 of teleprinter 590 so that this magnet can receive the message, connects positive battery to the upper terminal of magnet 548 to prevent the printer-reperforator from responding to the message, and operates busy relay 710. When the amount of type is reduced, by the retransmission of the first message, sufficiently to open contacts 682, relay 650 releases, and relay 651 operates to feed out the tape as before. At the end of the second message, the conditioning code opens contacts 591 to unlock relay 565. Call from subscriber B, Fig. 12, to distant manual exchange C, Fig. 16. The circuits are conditioned, i.e. relays 1262, 1306 operated, either by the conditioning code sent at the end of the preceding message or by keys 1201, 1331. Subscriber B first sends a series of " letters " signals to open contacts 1239 and release relay 1261 if operated. The station code C opens contacts 1232 releasing relay 1262 which energizes busy relay 830. The message followed by the conditioning code is recorded in printing- reperforator 1269 and relays 1261, 1262 are operated and the busy relay 710 released as before. Contacts 1212 operate relay 1303 to light lamp 1443, and the connecting relay 1448 is operated by the closure of key 1447, in the same manner as for a local call. The transmission circuit from distributer 1273 is extended to relay 1547 of a second printer-reperforator 1569 where the selecting code followed by the message is again recorded. A special operator at this position calls the operator at the distant exchange by throwing key 1686 which also starts the motor for the apparatus 1669, 1690. The special operator throws key 1695 to enable her to communicate with the distant operator by means of her teleprinter 1690 and to operate relay 1697. When the connection has been extended to the wanted destination, the operator closes switch 1580 to start the distributer 1573 for retransmission of the stored message over line 1629. The distant operator may break in on a transmission by causing contacts 1695 to operate, releasing relay 1697 and stopping the distributer 1573. The local operator opens switch 1580, restores contacts 1695 to receiving position, feeds back tape 1500 and then recloses switch 1580 to repeat the transmissi