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.
Found in a 1967 Electronics World, this circuit can use any modern equivalent FET. Observe the...
Found in American documentation from the 90's, this circuit applies to other operational...
This circuit was obtained from the February 1992 Radio Electronics magazine. In it, a bar of 4...