This receiver of two transistors for the 3.5 MHz band was found in a circuit manual from the 80's. The coil data are found next to the diagram and the transistors can be general purpose PNP.
We find this microphone voice effect in 1992 documentation. The vibration of the relay contacts...
This circuit for the car uses LDRs as sensors and does not need to be connected to the lamp. The...
Found in a Popular Electronics from the 90s, this circuit can be made with current equivalent...