Obtained from a 1969 documentation, this circuit can operate at frequencies up to 500 Hz, counting up to 999. The circuit makes use of neon lamps of the time.
This circuit can source up to 1,000 V from a 9 V battery. Output current is very low, some...
This circuit detects the presence of strong signals from spy transmitters, enabling their...
This circuit of a publication from the 70's uses a different type of power that we had already...