More VSS

[Mike Turner]

This sounds like a perfect place for a PIC. Since the pulse rate is really
low by microprocessor standards, any normal speed PIC should work. If a
duty cycle close to 50% is important, as several other people have
indicated, the PIC could look for an edge and deliver a pulse half the
duration from the previous edge. Startup (or is it stopping?) is
interesting but the rest appears simple. Admittedly, it's not a perfect
duplication of a clipped and squared AC generator output but it's darn
close. Or is this a waste since it reduces the circuit to only 2 IC's: the
PIC and a regulator? A crystal and bypass caps are needed for the PIC.
Don't forget bypass caps for the TTL circuit earlier in this thread!. Noise
and transient suppression on circuit I/O pins would be strong wants for
either circuit as would a quiet rugged power source.