scope:

GENERAL

This unit is intended for use at Barrier Level Crossings where a number of flashing road signals are provided. The road signal includes two lamps side by side which flash in antiphase. The flasher unit shall therefore supply two outputs, one to each phase of the flashing road signal.

The failure modes of the unit shall be such that failure to flash will result in at least 50% of the lamps giving a steady light. Failure of all lamps on one output shall not affect the flashing rate of the other output.