This circuit was found in a 80’s American documentation. The adjustment trimpot is from 47k to 100k. The diodes are general-purpose types use and the supply voltage depends on the relay.
This circuit is intended to reinforce old car radios, having been found in 1997. At that time,...
The Sample and Hold circuit shown in the figure was found in a 1994 Linear Applications Handbook by...
Found in a 1980s documentation, this circuit detects when the voltage drops below 11 V. Other...