The frequency of this circuit depends on the crystal. The transistor supports a modern equivalent. We found it in documentation from the 1980s.
This circuit was found in American documentation from the 1960s. The operational amplifier is from that...
This fuzz effect for guitars was found in an American 1980s documentation. The transistors may be the BC549...
This circuit has visual and audible status indication using an oscillator. The circuit is from a...