We found this circuit in the July 1994 Radio Electronics magazine. The circuit uses a general-purpose transistor, and the power supply can be up to 12 V depending on the relay.
This circuit was found in documentation from the 1980s requiring a variable power supply from 0 to...
This circuit is suggested by the Optoelectronics Sourcebook by Texas Instruments when AC signals...
This one-digit photometer using CMOS circuits was found in a 1989 documentation. The circuit is...