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 circuit was found in an English magazine from 1983, but it can be assembled with BC548. The...
This circuit tunes MW radios to apply the signal to a good audio amplifier. The circuit is from an...
The cascade connection of two flip-flops allows division by 4, as shown in the figure. Note that...