Patent GB-527336-A (GB)
Title: Printing telegraph system
IPC: H04L12/06
Filed: 1939-04-06
Abstract: 527,336. Telegraph exchange systems. STANDARD TELEPHONES & CABLES, Ltd. April 6, 1939, No. 10790. Convention date, April 6, 1938. [Class 40 (iii)] In a printing telegraph exchange system, the initiation of a supervisory signal (as by the depression of a key) causes the connection to a trunk circuit of a start-stop permutation code transmitter and the message permutation code signals are prevented from giving supervisory indications. The code transmitter for giving a disconnect signal d, Fig. 2, a recall signal r, and a call signal c, has fourteen segments 1 ... 14 but revolves at half the speed of a standard five-unit start-stop distributer, shown above. The first and seventh segments of the signal distributers are always spacing and the second to fifth, the eighth and tenth to fourteenth always marking. The differentiation occurs at the sixth and ninth segments. Setting up connection between two stations. A call from subscriber A, is answered by inserting an answering plug 402 in jack 403 to operate relays 406, 405, if this cord circuit is the first to complete the sleeve circuit, and lock relays 406, 409. The relay 406 operates a relay 502 which operates whenever the answering or calling plug is inserted in an associated jack and grounds balancing network 503, 504. A circuit, shown in thick lines, extends from the answering side of the repeater to the ring conductor of the answering plug. Operation of an operator's printing-telegraph key 411 operates a relay 419 followed by a relay 413, which holds the relay 419 and operates a slow-acting relay 420. The operators' printing telegraph set 600, Fig. 6, is now in the communication circuit. When the printing- telegraph key 411 is restored, the relay 413 releases before the relay 419 to replace a resistance 522 before the telegraph set is disconnected and thus insure that transmission through the repeater is not interrupted. The relay 413 also enables a relay 433 to respond to a relay 435, which was operated when the plug 402 was inserted in the jack 403. Upon receiving the called number, the operator inserts a calling plug 539 in an idle intertoll trunk jack 705, Fig. 7. A relay 511 operates and hence a relay 512 which completes a circuit to the repeater relays 505, 514 and transfers the tip conductor of the plug 539 from tip busy test conductors 525, 604 to a calling supervisory circuit to operate a relay 515 which locks and operates a relay 516, a supervisory call lamp 526, and a relay 529 for a pilot lamp 530. When the plug 539 is fully inserted, the relay 515 releases and the lamp 526 flashes until the operator opens the communication circuit. When the operator operates a ring key 429 to the right, a ringing relay 513 opens the communication circuit from the intertoll trunk line 7001, but the calling side of the repeater is still connected to hold the calling subscriber's circuit A and the operator's printing telegraph set closed. While the ring key is held operated for two or more seconds, a rotary switch, not shown, at an exchange C, Fig. 7, flashes a lamp and then automatically releases. The relay 513 also operates a relay 520, which locks, lights a guard lamp 533, closes the calling side of the repeater, and releases relays 515, 516 to extinguish the lamps 526, 530. When the operator at the exchange C plugs the answering end of a cord circuit 701 in a jack 706, the relay 520 releases, the ringing guard lamp is extinguished and transmission can take place. On receiving the number of the called subscriber D the operator at the exchange C completes the connection with the calling end of the cord circuit 701. Sending supervisory signals from exchange B, Fig. 6. The operator closes a supervisory signal key c, r or d. The call key c, for example, operates relays 610, 626, 627, 628, the two latter locking. The relay 626 operates a final prepare relay 631, which locks, and the relay 610 connects a conductor 611 to the upper opened contact of the relay 626 so that a spacing signal is repeated to a relay 708 at the exchange C and thus operates a slow-acting relay 709. On the release of the key c, the relay 626 is restored, a start magnet 634 energized, and an inductance 633 ensures that a marking signal is transmitted to the toll line. When the shaft 619A begins to rotate, the contact of a cam 622 opens to transmit the first spacing signal, Fig. 2. Subsequent closures and openings by cams 620, 621, 622 control the line circuit and are repeated by the relay 505 to the receiving exchange C. During the tenth signal interval, the contacts of a cam 623 open to release the relays 631, 627, 628, 610, but the consequent opening of the line circuit is not sufficiently long to affect the receiver, and the start magnet 634 is released to stop the shaft at the end of its revolution. The recall key r acts similarly, but the selector relay 628 does not operate and the closure of the contacts of the cam 620 at the ninth interval is ineffective. In the case of the disconnect key d, the relay 627 does not operate and the closure of the contacts of the cam 621 at the sixth interval is ineffective. Receiving supervisory signals, Fig. 7. The relay 709 operates on a spacing signal slightly longer than the longest in the ordinary 5-unit code, and then operates a prepare relay 710 which locks and enables the toll line, when subsequently closed, to operate a relay 712. The latter locks and substitutes the battery on the armature of the relay 708 for that on the lefthand back contacts of the relay 712 in the circuit of a selecting magnet 713, which now operates in accordance with the 14-unit impulses. The first spacing impulse releases an armature 714 to permit a shaft 716 to rotate in synchronism with the start-stop shaft 619A at the exchange B. Cams 723, 722, 721, 720 engage their respectively associated operating levers 730, 729, 728, 727 during the sixth, seventh, eighth and ninth intervals respectively, but the corresponding T levers 737, 740 are only operated when an armature extension 732 is released by the magnet 713. Code bars 741 ... 744 are thus operated in accordance with the received signal and close corresponding contacts 745 ... 748. The call signal, for example, operates only the contacts 747 and a relay 751 consequently lights a call lamp 726 until the operator opens a switch 754. At the tenth interval a cam 749 operates contacts 750 to operate a relay 711 which releases the relays 710, 712, and at the end of the revolution the magnet 713, stops a cam 715. A disconnect signal operates code bars 743, 744 to operate a relay 752 which locks and lights a disconnect lamp 725. A recall signal operates the code bars 741, 743, to operate the relays 751, 752, which lock and light a recall lamp 724.