Found in American documentation, this circuit can be used as a shield. The technology is CMOS and the input is BDC. Next to the diagram formulas for calculating the components.
This circuit from a Radio Electronics from February 1966 uses an LDR as a sensor. The transistor is a...
This circuit found in Electronics Handbook, Volume XIII 1993 shows a simple configuration of a...
This configuration found in GE documentation from the 90s, can also be seen elsewhere in this...