This 5.1 MHz circuit was found in a 1980s documentation. The frequency is given by the crystal and general purpose transistors can be used.
This didactic circuit was found in an English publication of 1965. The sensor is an LDR and...
This micro FM transmitter uses a tunnel diode as an oscillator. I found it in an English...
This bistable control uses a 4069 as bistable. The circuit can drive relays up to 100 mA with the...