General Electric suggests this circuit in a 1980s documentation. The operational of the time is FET-type input. Modern equivalents may be used.
In the figure we have a very low current DC to DC converter using a 555. The circuit can have...
A divide-by-4 or two-bit binary counter can also be built using two flip-flops of the 4027 type as...
This circuit can be used as a buzzer from 3 different locations, allowing you to identify where it went...