We found this circuit in the July 1971 Radio Electronics magazine. The circuit activates a Sonalert or a relay for a higher power warning system.
This small audio amplifier was found in the May 1994 issue of Electronics Now magazine. The power...
The displayed relay operates with an audio signal applied to the input. The transistors can be...
The circuit shown in the figure and uses the diode in the leakage current operation mode. In it,...