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.
In the figure we have the way to use a common operational amplifier for AC signals. The resistor...
This configuration presents a negative resistance caracteristic such as the one found in...
The transistors of this circuit found in a 1965 magazine can be the BC558 and the sensitive 12 V x...