Thanks Robin

The problem is it *is* working in as much as the led is on all the time instead of off until flashed. I checked Mach and the output flashes in the diagnostics screen. I'll reconfigure the circuit again (have tried 4 transistors so far) with one of the last 10 transistors I have. I'll also get a 24v lamp to test it if I can find one today.

Cheers
Bruce