This circuit was obtained from a Radio Electronics issue from January 1989. The indicator is a ceramic transducer, and the frequency of the emitted sound is given by C3.
This keypad telephone encoder circuit was found in ancient American documentation. The components used...
At each switch position, a diode is connected in series with the motor, thus causing a small...
The passage of an object in front of the LDR, producing a shadow or even turning off the ambient...