Found in a 80s American documentation, this circuit pulses a lamp for optical relay tests. The circuit can be modified to trigger a high brightness white LED.
This indicator for audio signals uses only 3 components. LEDs are common and the audio signal with...
Found in American documentation from the 1980s, this circuit uses transistors from that time. It...
This circuit for audio signals was found in the March 1990 Radio Electronics magazine. The circuit...