This circuit makes use of a low impedance microphone. The relay is according to the supply voltage which can be between 9 and 15 V. The operational gain is approximately 100.
We found this circuit in the July 1969 Radio Electronics magazine. The circuit uses a coupler made...
With the configuration shown in the figure, a common 12 V lamp lights up when light no longer...
This oscillator has its frequency controlled by crystal and its frequency can be between 100 kHz...