Optical shield (CB20698E)

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

Optical Receiver Shield (CB19865E)
Originally this circuit was indicated to be used in a garage door control, but it can be modified for...
400 Hz 741 Oscillator (CB17028E)
This conventional oscillator with the 741 can be precisely adjusted to produce a 400 Hz signal. The...
Variable voltage regulator (CB21192E)
This current-limited circuit was found in a Popular Electronics from the 90's. ...