Patent GB-740085-A (GB)
Title: Facsimile telegraph systems
IPC: H04N1/42
Filed: 1952-07-11
Abstract: 740,085. Facsimile telegraphy. CREED & CO., Ltd. July 11, 1952 [July 24, 1951], No. 17573/52. Class 40 (3). At the end of facsimile transmission from a subscriber to a main office, machines at both stations are automatically stopped and the main-office operator, after checking the received message for legibility, sends a special acknowledgment signal to the subscriber's station. The acknowledgment signal is of special frequency and an electric device tuned thereto at the subscriber's station causes the operation of a visual signal which remains illuminated after the cessation of the signal frequency until it is switched off. In the case of transmission from the main office to the subscriber, the latter may send an acknowledgment signal, indicating satisfactory transmission, or a " re-run " signal asking for transmission to be repeated. In the two-way system described, the subscriber has combined transmitter-receiver equipment, Figs. 3, 4, of the kind described in Specification 723,352. The line L1, L2 terminates at the main office in a jack PJ, Fig. 2, into which the operator may plug a transmitter, Fig. 1, of the kind described in Specification 677,040 or a recorder, Fig. 2, of the kind described in Specification 680,661. Call from subscriber to main office. Operation of send-button 206, Fig. 3, energizes (from A.C. mains A, B) power relay PWR which connects mains lead A to lead A<SP>1</SP> and energizes drum motor DRM, chopper-disc motor CHM, exciter lamp 204, transmitting amplifier AMT and relay TR. Ground at contact 266 is connected over contact 262 and rectifier 228 to a simplex circuit on line L1, L2 causing the operation of relay CLR, Fig. 2, to light calling lamp 20 and common visual and audible signals 27, 28. Insertion of plug RG and operation of start key 138 extends the ground on the simplex circuit to relay RPU which operates relay RH. Relay RH energizes relay RPR to start the stylus-band motor SM and short-circuits normally-energized relay RM which releases to remove a short-circuit from relay RPH. At the subscriber's station relay HR operates slowly in the circuit of valve 270 of the receiving amplifier AMR (to allow motor DRM to attain full speed) and removes the short-circuit at contact 266 from commutator contacts 267 so that relay RPU, Fig. 2, is pulsed once per revolution of drum 200 (for phasing purposes). At the first release of relay RPU, the last short-circuit is removed from relay RPH which operates to remove a short-circuit from the output of amplifier MP, to start the paper-feed motor PFM and to energize phase magnet PMR which replaces negative battery B15 on the simplex circuit by positive battery B20 causing the operation of line relay LR, Fig. 4, over rectifier 230. Magnet PMR also releases the stylus belt 130 for drive by motor SM. Relay LR at the substation connects up drum-feed motor DFM and scanning commences. At the end of the transmission, send-button 206 is automatically released by the scanning carriage, power is taken off the apparatus, and the simplex circuit is no longer pulsed. At the main office, permanent disconnection of negative battery B16 from the control grid of valve VT<SP>1</SP> renders the valve operative to energize relay REM to stop the mechanism and light end-ofmessage lamp 168. The operator feeds out a length of paper, whereby relay REM is released by contact 170, and if the message is satisfactory code transmitter CD is operated to send an acknowledgment signal and the plug RG is withdrawn. The acknowledgment signal of a special frequency is sent back over the simplex circuit and controls through a tuned transformer or a vibrating reed the' illumination of a cold-cathode discharge tube. Call from main office to subscriber. Insertion of a drum 30, Fig. 1, carrying a message 31 releases relay TD and relay TPR operates to energize drum motor DM, chopper-disc motor CM and lamp 38, and to release half-nut magnet HN. Insertion of plug TG, Fig. 1, into jack PJ, Fig. 2, and momentary operation of start button SB causes the operation of slowrelease relay SR from positive battery B4, followed on the release of button SB by the connection of negative battery B5 (before relay SR releases), over the sleeve and ring contacts to the starting electrode 81 of tube 80 which fires and operates relay TS. Positive battery B4 is now connected over relay TPU to the simplex circuit operating the subscriber's line relay LR. Operation of receive button 208 energizes power relay PWR to start drum motor DRM and energize receiving amplifier AMR. The operation of relay HR energizes stylus motor STM and drum-feed motor DFM and opens contact 266 to cause the simplex circuit to be pulesd. When relay TPU first operates it energizes relay TH which lights lamp 87 and opens the circuit of the left-hand winding of normally-operated relay TPH. At the first pulse through relay TPU, the locking circuit through the right-hand winding of relay TPH is opened and the relay releases, opening a shortcircuit across output wires 54, 55 and energizing phase magnet PMT which clutches the drum 30 to the drum motor to start transmission. At the end of transmission closure of contacts 43 by the scanning carriage 36 or of contacts 431 through a hole 311 punched in the paper 31 after the end of the message energizes relay TEM to release magnet PMT whereby the scanning carriage is returned to its normal position. Relay TEM replaces positive battery on the simplex circuit by negative battery through the right-hand winding of relay TRR but this relay is unable to operate over resistance 263, Fig. 4. The subscriber's line relay LR is released, relay ACK and neon lamp 304, Fig. 3, are operated and buzzer 290 sounds. Operation of stop button 210 energizes relay BR to cut off the buzzer and restore button 208. If the nessage is satisfactorily received, operation of acknowledgment button 305 releases relay ACK and removes ground from the simplex circuit so that relays TPU, TH, Fig. 1, release and acknowledge lamp 105 is lit. If the subscriber wishes a retransmission he presses re-run button RB which short-circuits resistance 263 so that relay TRR operates and lights re-run lamp 125. Faulty operation. If the subscriber's drum stops during transmission, relay TPU is no longer pulsed, valve VT energizes and relay TPH operates to disconnect magnet PMT causing the operator's machine to stop indicating a fault. If the subscriber presses the send button in response to a call from the main office, relay HR is short-circuited over contact 336 of receive button 208 and the buzzer is connected up over leads 293, 340 nad contact 342. If he presses the receive button when making a call, relay HR is short-circuited over contacts 346, 350 and the buzzer is operated over leads 293, 354, and contact 356. If the subscriber is initiating a call when the operator presses start button SB to send to him, the negative battery B5 has a shunt path to ground at the substation so that tube 80 is unable to fire, and the operator changes over his apparatus to receive the subscriber's message.