Circuitron ~ Heavy Duty Alternating Grade Crossing Flasher ~ FL-2HD ~ 5122

Circuitron ~ Heavy Duty Alternating Grade Crossing Flasher ~ FL-2HD ~ 5122

GENERAL DESCRIPTION: The CIRCUITRON FL-2 / FL-2HD is a complete solid state flasher that will
alternately flash two 250 ma. loads ( 500 ma. for FL-2HD ). The FL-2 / FL-2HD contains on-board
regulation to allow the unit to be powered by 10 – 18 volts AC or DC, and has a control terminal for
use with CIRCUITRON detection circuits. Mounting pads are provided on all four corners of the
printed circuit board, or the board may be mounted by snapping it into a section of CIRCUITRON’s
Printed Circuit Mounting Track ( PCMT ).

CIRCUIT DESIGN: The CIRCUITRON FL-2 / FL-2HD utilizes a low-power CMOS integrated circuit
connected as a free-running astable multivibrator. A diode in conjunction with a zener and a filter
capacitor provide a source of filtered DC for the IC. The complementary outputs from the integrated
circuit drive two transistors (Q1 & Q2). A ground connection on the control terminal (C) enables
output from the IC to the transistors. Returns from the loads are alternately grounded by Q1 and Q2
connected common emitter.