Using a house fire alarm to shut-off a power outlet. The circuit uses transistors in a latching fashion, such that anything can happen to the fire alarm once triggered, it can stop or burn, the circuit will remain latched and the power outlet will not be conducting. Until the user comes and reset the unit. The circuit uses a photo-isolator between the fire alarm and the circuit, 4 transistors and a 16A relay for the power outlet. The photo-isolator allows an alarm unit to provide a trigger at a voltage up to 30V and also ensures that a voltage spike from the fire alarm will not cause further harm to the circuit, in case the fire alarm short circuits or burns for example.

Jumpers JP1A and JP2B are available in case external indicators already contain their needed resistors. In such case, the jumper should be shorted.