Found in American documentation from the 90s, this circuit has the signal frequency determined by capacitors from C4, C3, C2 and C5 selected by digital switches.
Found in documentation from the 1980s, this circuit can have several adaptations to use modern...
This receiver for listening to the TR-23 phone was manufactured in Japan in the 1960s. The circuit is...
The frequency of the tone produced by this oscillator depends on the amount of light falling onto...