This circuit protects the speaker from dangerous direct currents that could damage it. The circuit is from an Electronics Experimenter Handbook 1993 edition.
This circuit was found in a 1986 documentation and can use any operational amplifier like the 741...
The sensor for this circuit found in a 1980 publication is a common LED. The LED can sense both...
This 25 W phase photo control was found in a 1965 General Electric publication. The circuit uses a...