Optical shield (CB20698E)

This circuit was found in American documentation from the 90s. The coupler is the type that uses a photo-Darlington.

Digitally Controlled Filter (CB14368E)
We found this circuit in the Linear Applications Handbook by National Semiconductor. The circuit is...
Radiation monitor (CB5923E)
This wide-range radiation monitor was found in a 1980s documentation. The circuit uses a diode as a...
Guitar Preamplifier (CB24305E)
This circuit is from an article that appeared in the June 1974 issue of Radio Electronics...