This circuit was obtained from 1967 documentation. It uses a sensor to determine the trigger point. The components are of the time, difficulty to obtain these days.
This circuit, found in documentation from the 1980s, uses an operational amplifier from that time....
This low frequency sinusoidal oscillator was obtained in documentation from the 1970s. Operational...
This circuit was found in a 1980s documentation. It is intended for remote vibration monitoring...