This timer, like the previous circuits, uses a currently uncommon integrated circuit. The time is given by capacitor C1 and R2 which has the range of values indicated in the diagram.
Found in a Hands On Electronics from the 80's, this circuit activates a relay with alternating...
The frequency of this circuit, that makes use of a tunnel diode as an active element, depends on...
Found in 1980s Electronic Engineering, this circuit uses common phototransistors as sensors. The...