Flashing signal for railway crossings

A system of red and green warning-lamps for use at railway crossings in Belgium is described, in which flashing is achieved without mechanical interrupters. The lamps are connected across the mains supply in series with a transformer primary winding and a choke. The transformer secondary is included in the circuit of a Ne-tube relaxation oscillator and the resulting current pulses reduce the primary inductance and make the signal lamp flash. A feedback voltage taken from across the choke enhances the effect. The approach of a train de-energizes a relay and switches the system from green to red.