This alarm siren circuit has a latch. We found it in an article in the January 1975 Radio Electronics magazine. Note the power given by Rx and the speaker. It can be increased by changing Q1.
This small FM transmitter for clandestine listening has a good range and should be powered by a 9...
This circuit has a high input impedance and provides a good signal at its output. The power must...
This traditional metronome configuration uses unusual transistors in the original version, but it...