Inside the Apocalyptic Soviet Doomsday Machine

Actually very easy. If no civilian fm or am radio stations are heard by such a system for four months to a year a automatic launch could happen.

Making sure the system had a antenna thats screwup proof would mean the system would have line running to a former coal mine or be in one several miles down.

The small unused coal veins would provide the antennas and protect against a space nuclear electromagnetic pulse that would fry the delicate robot brain.