This circuit was found in a 1969 US documentation. It provides a signal that can be externally programmed as suggested circuits. The circuit can be used as a shield.
This crystal-controlled circuit with 60 mW output power is in the Radio Electronics magazine of...
This circuit is from an old American documentation, from 1977, but it can be implemented with more...
This is a commercial circuit found in Radio Electronics magazine from September 1960. The circuit has...