Patent GB-1161383-A (GB)
Title: Improvements in or relating to Electrical Signalling
IPC: G08G1/16
Filed: 1967-08-30
Abstract: 1,161,383. Radio signalling. F. W. L. DEITENBACH. 30 Aug., 1967, No. 39688/67. Heading H4L. In a radio-frequency two-way inter-vehicular signalling system each vehicle comprises a transmitter, a receiver and an indicating signalling means, all adapted for use with three different types of signals representing, respectively, a calling signal, a warning signal and a permitting signal. As described, a mobile installation 10, Fig. 1, comprises receiving equipment 12 having a receiver 16 and audio amplifier 18 with output to a multi-frequency reed relay unit 20, which operates relays 22, 24, 26 according to the frequency of received signals, so that appropriate indicating lamps are lit. The installation also comprises a transmitter 14 having a modulator 30 connected to a final output stage 36 and fed by an R.F. oscillator 28 and a tone generator 34. A switch unit 42 controls the tone generator 34. In the receiving equipment 12, Fig. 2, the multi-frequency reed relay unit 20 closes one of three contacts 50, 52, 54 according to the frequency of the received tone. These contacts respectively control the operation of relays 22, 24, 26, the contacts of which respectively control the lighting of pairs of lamps 60 (red), 58 (amber), 56 (green). The contacts of the relays are interconnected so that the lamps 56 and 58 are disconnected when the relay 22 is energized and the lamps 56 are disconnected when the relay 24 is energized. The amber lamps 58, which are used to indicate a calling signal, may be paralleled by buzzer 62. In the transmitter 14, Fig. 3, the switch unit 42 comprises three switches 78, 80, 82. When a switch is operated one pole connects power via a lead 70 to the oscillator 28, the output stage 36, the modulator 30 and the tone generator 34. Another pole of the operated switch connects to the tone generator 34 one of three differently tuned resonant circuits 84, 86, 88 whereby a modulating frequency appropriate to select the desired signal lamp at the receiving station or stations is produced. An emergency switch 43.1 is provided which causes the operation of a selfhold relay 32. This relay operates a pulse relay 71 which connects power in an on-off sequence to the lead 70 and it also connects the tuned circuit 84, corresponding to the red indication, to the tone generator 34. The relay 32 may be released by operating the switch 78. The emergency switch 43.1 is paralleled by a shock switch 43.2, which is operated automatically in the event of the vehicle experiencing a heavy collision. A power supply unit (Fig. 4, not shown) for connection to a vehicle battery comprises a smoothing circuit, a dropping resistance for switching in for 12 or 24 volt operation, and a power transistor controlled by a zener diode for voltage stabilization. A fixed station transmitter and an associated mains power supply unit are described (Figs. 5, 6, not shown) and also a transportable transmitter powered by dry batteries or an accumulator which may be charged by solar cells (Figs. 7, 8, not shown). The circuitry is generally similar to Fig. 3, but the self-hold relay 32 &c. are omitted. Test apparatus 140, Fig. 9, for the system comprises receiving equipment 144 and transmitting equipment 142 either of which may be connected to an aerial 176 and a battery 172 by interconnected switches, and a meter 146. When testing a mobile station receiver, using the equipment 142, the operation of press switches 180, 182, 184 operates a tone generator 156 so that the indicator lamps 60 or 58 or 56 at the mobile station are lit. When testing a mobile station transmitter, using the equipment 144, lamps 196 or 198 or 200 in the test apparatus are lit, according to the modulating tone of the signal from the mobile station. The meter 146 may be connected by a switch 178 to the battery 172 to check its condition. During reception of a distant station the meter 146 is connected to an automatic gain control resistor (210), Fig. 10 (not shown), so that it indicates received signal strength. Means are also provided for direct connection of a transmitter to the test apparatus, when the meter 146 is used to measure power output and modulation level.