Found on 90's Popular Electronics, this circuit triggers when the microphone picks up a sound. The circuit is powered by 9 V but will also work at 12 V by triggering a relay instead of the buzzer.
This small FM transmitter can be powered by solar cells in the range of 1.2 V to 6 V. Its range...
The duration of the output pulse in this circuit depends on C. This capacitor can have values in...
This very low power amplifier is designed by Amperex for hearing aids. It is based on TAA370 which is...