Optical shield (CB20698E)

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

Timer 4011 (CB19630E)
The outputs of this timer or CMOS timer configuration with the 4011 integrated can be connected to load...
FM Transmitter with a Tunnel Diode (CB12230E)
This micro FM transmitter uses a tunnel diode as an oscillator. I found it in an English...
Low Resistance Continuity Test (CB5934E)
We found this circuit in a 1980s publication. The circuit, however, makes use of common components...