This code practice circuit was found in a 1990s issue of Radio Amaterur Today magazine. It produces an audio tone with the 555.
This oscillator can generate signals from 100 kHz to more than 50 MHz depending on the crystal used...
Found in a 1980s American documentation, this circuit appears with variations elsewhere in this...
This circuit was obtained in a 1969 documentation. The circuit modulates both the emitter current and...