Description

The SCR490D is used to provide remote monitoring of steady

burning incandescent marker and obstruction lighting. Four

onboard switches allow operator programming for lighting

systems with two through nine lamps on a single AC circuit. The

SCR490D uses a toroidal sensor and electronic circuitry to sense

the failure of one or more lamps.

Operation

When a lamp fails, the SCR490D senses a decrease in current

flow. Then, after a fixed time delay, it transfers to its alarm mode.

In alarm mode, the LED indicator, the output relay (SPDT

isolated contacts), and a non-isolated solid-state output are

energized. Replacement of the failed lamps resets the alarm

outputs and the LED indicator. To prevent false alarm signals,

power must be applied to the SCR490D at the same time that

lamps are energized.