The time of this timer depends on C1. The circuit was found in the July 1994 Electronics Now magazine. The supply voltage depends on the relay and can go up to 12 V.
With the configuration shown in the figure, a single pulse for a counter can be obtained from a...
With calibrated RV1 it is possible to find a zener diode voltage. The integrated circuit is 0 741...
This circuit was found on an 80's Ham Radio. The transistor admits equivalent. The circuit can...