This circuit is from a factory manual from the 80s. The circuit can be implemented with more modern operationals. Capacitor C1 is a low leakage type. The power supply must be symmetrical.
This circuit was found in an Electronic Design from 1967. The circuit uses two triacs being T2...
Found in old American documentation, this circuit can use crystals between 27.5 and 33 MHz...
This shield from the 60's uses a germanium transistor of the time and a common type of relay of...