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 circuit was found in a 1964 MOSFET applications manual. The circuit uses period general...
This circuit is from a Japanese documentation from 1971, using transistors of the time. The...
This circuit uses Only passive components and have to be plugged to the input of an audio...