This circuit was found in an Electronics Now from the 90's. The integrated regulator circuit and the power transistor must be equipped with heat radiators.
This 1968 Mullard circuit detects fire by smoke using LDR-type sensors. The circuit makes use of...
Found in the American 73 magazine for radio amateurs, this circuit can test common quartz...
With this circuit it is possible to tune the signals in the 50 MHz band in a common AM receiver around...