Found in a 1992 book, this circuit is intended for operation with audio signals. Equivalent operational amplifiers can be used. The optical coupler is an unusual type today.
The circuit shown in the figure is suggested by Intersil (www.intersil.com) and makes use of the...
We found this version of the automotive tachometer in a 1980s publication. Variations from other...
The battery charger shown in the figure uses two 60 W incandescent bulbs in series to limit the...