Found in an American 1980s documentation, this circuit compares signals from two TTL sources, providing an output that depends on the frequency difference. The circuit can be used as a shield.
This circuit is from a 1972 Motorola publication. Some of the used transistors can still be found,...
This circuit controls 6 LEDs in two sets with the phase change cycles controlled by a 555...
Originally created to power an 80's RTTY printer, this circuit can be used in other applications. The...