Patent GB-786386-A (GB)
Title: Improvements in or relating to systems for guarding the transmission of messages
IPC: H04L1/00
Filed: 1955-08-29
Abstract: 786,386. Printing - telegraph systems. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Aug. 29, 1955 [Sept. 1, 1954], No. 24725/55. Class 40 (3). In a system for supervising the transmission of messages from a first station to a second station in which the message is terminated by a clearing signal which brings the transmission path to a rest condition and in which each station includes a clearing signal detector, the second station on the operation of its detector sends a service signal to the first station, warning means is operated at the first station if it does not receive a service signal within a predetermined time after response of its clearing signal detector and the second station includes warning means which respond if the characteristic rest state is imposed on the transmission path without the response of the clearing signal detector at the second station. In the rest condition a device LZ at the transmitter repeats the rest signal " letters " via released contacts a2, b2 to the transmitter ZA. To initiate transmission the closure of a key stt operates a relay B which locks up and at contact b2 applies a start signal from transmitter TZ. At the receiver station, Fig. 1b the start signal is detected at TD which operates a relay TS closing at contact tsl the circuit of magnet DM by an interrupter RU so that a preselector VK finds an idle reperforator RO and the operation of relays P, C in series connects at p7 the busied reperforator to the receiver OB and at p8 opens the circuit of the stepping magnet DM. Relay DG operated over contacts p4, ts3, locks up and at contact dg2 brings in transmitter ZB which sends to station SA a service signal indicating that it is ready to receive and operating, at station SA, a relay DR which at contact dr1 closes the circuit of relay A over contact pc closed when tape has been inserted in the transmitter BZ. Relay A locks up over contact a5 and at contact a1 operates the transmitter BZ which prefixes the message by a letters signal operating detector LD, Fig. 1b so that relay LR operates and at contact lr1 opens the circuit of relay DG which releases and at dg2 cuts off the transmitter ZB. The end-of-message code signal combination is constituted by " letters," " figures," and the letter D and is detected by the circuit arrangement, Fig. 2. The first signal closes contacts pa1 . . . pa5 and operates relay LE which locks up over winding LE2. When the reperforator receives the next signal an impulse is applied at IM to the winding LE3 in the opposite sense but relay LE temporarily remains energized. The " figures" signal-closes contacts pal, pa4, pa2, pa5 and energizes relay CY which locks up over contact cy1 and contact le4 (released). On the next testing impulse relay LE releases and the final signal " D " operates contacts pal, pa4 energizing winding DB1 of relay DB which locks up through contact db1 and its second winding. At the transmitting station a relay DA in the detector MA is operated by the end-of-message signal and at contact da1 connects capacitor CC to the winding A1 so that relay A deenergizes after a short delay, opening the circuit of relay DA and also cutting out the transmitter BZ so that the signal " letters " is again transmitted from LZ. At the receiving station SB, the operated contact db2 opens the circuits of relays C, P so that a circuit is completed for relay DG1 over contacts u2, p4 and delayed contact pv1. At dg2, the transmitter ZB of station SB sends the service signal operating relay DR at station SA so that SR is operated and locks up. If the service signal is not sent, relay SR is not operated, a circuit is completed for relay LA over contact sr2 contact a7 and delayed-release contact av1. The relay LA can be arranged to operate an acoustic or visual warning. If it is assumed that the signal detector MB at the receiving station has not operated relay DB, relay P remains operated and the repeated transmission of " letters " from the station SA operates LD and relay LS so that a number of operations of the integrating circuit VN causes tube GB to strike and operate relay U which opens the circuit of relays C, P. An alarm relay LB operated over contacts db3, c2, and delayed-release contact cvl locks over contact lb and operates an acoustic or visual warning d vice. If, at the transmitter station, the tape breaks ol is exhausted, contact pc opens and releases relay A with consequent operation of the alarm relays LA, LB at the stations SA, SB. Specification 777,195 is referred to.