This circuit turns off a relay after a time determined by C1. The circuit was found in the December 1974 Radio Electronics magazine. The relay is rated according to the supply voltage.
Using components from the era, this 90's EDN circuit is used in analog to digital conversion...
Found in an American publication from the 90s, this circuit allows the supply of 3, 6 and 9 V...
We found this circuit in an old Popular Electronics. The circuit is experimental, driving an LED...