This circuit was found in an Electronics World of 1968. Its purpose in triggering a relay when the circuit receives signals from a vibration sensor. The circuit is used in emergency situations.
This circuit for signals around 4.5 MHz for old analog TV was found in the September 1992 Radio...
The circuit shown is a commercial electronic voltmeter sold in Japan in the 1960s. The circuit is fully...
This 80's circuit can be implemented with modern equivalent FETs with lower on resistance. The...