This triac circuit turns on a load after a time of 8 to 80 seconds adjusted by potentiometer R7. The circuit is from a Radio Electronics from June 1970.
Found in a 90s Popular Electronics, this circuit uses two PLL tone recognizers to trigger by touch an...
This Hughes circuit is from 1968. Equivalent modern components can be used. The input impedance is...
This circuit is from 1995 documentation. In the original, the source is symmetrical at 12 V, but...