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.
This other comparator configuration with AD using the R / 2R network is from factory documentation from the...
This circuit can be controlled by pin 1 through the output of a microcontroller functioning as a...
This very simple circuit must use coal microphones of the type found in very old equipment. The...