GB1437111A - Navigational aid system - Google Patents

Abstract

1437111 Pulse circuits AUTOMATIC POWER Inc 5 Sept 1973 41857/73 Heading H3T [Also in Division G4] A set of buoys have their lamps switched on in synchronism or sequence by respective monostable circuits 18 triggered by pulses from a counter 16 driven by one-second pulses from a master oscillator source 15 and synchronism of the counters is effected by receipt of radiated signals. These signals comprise a 100 Hz toneburst of 10 seconds and if a sync. signal detector 21 at the buoy detects a burst longer than a given duration it produces a counter reset pulse at the end of the burst. The sync. signal detector Fig. 3 produces a pulse E only if input D is at least eight seconds long: during pulse D a capacitor C1 is charged by a circuit which includes a transistor-inverter Q1 and a transistor Q2, the voltage at the base of the latter being low thereby biasing it off and voltage on capacitor C1 rises. When such voltage reaches a predetermined level, set by a Zener diode Z1 to correspond to charging for eight seconds, a pulse E is produced and continues for the remainder of the time pulse D is present. Signal E turns on a transistor Q3 and transistors Q4, Q5 turn on. A negative spike F is produced at the trailing edge of pulse D by a capacitor C2 to briefly turn off transistor Q5 thereby producing a positive pulse C to simultaneously reset each stage of counter 16, Fig. 2. Thus all buoys flash simultaneously despite oscillator 15 stability not being very high. The radio signal may be emitted from a "master" buoy, the output pulse A keying a tone modulator, Fig. 4 (not shown). Sequential light emissions are effected by a delay circuit between counter 16 and multivibrator 18, Fig. 6 (not shown).