Found in an old American documentation this FM modulator makes use of a varactor diode. The circuit can be easily implemented given the small number of components used.
The critical components for this 1970s project are transformers. The original transistors are made...
Found in a 90s Popular Electronics, this circuit keeps an LED on when a phone is in use. Can be...
We found this frequency meter circuit in a 1974 documentation. The circuit is powered by 12 V and...