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 was found in an EDN from the 90s. For the components indicated, the frequency is 10 kHz....
This circuit provides voltages and a 1 kHz signal for measurement bridges. The circuit is from...
We found this circuit in an old documentation, but it is still current. General purpose...