This circuit activates a relay after a time given by C1 and R1. The circuit is from a Radio Electronics from December 1974. The relay voltage is the same as that used in the power supply.
In the figure we have a simple logic level indicator for TTL circuits or powered by 5 V....
This circuit was obtained from the December 1990 issue of Radio Electronics magazine. The circuit...
This power supply for gas laser (HeNe) was found in a 90’s Popular Electronics. It generates from 1300...