This circuit is from the National Semiconductor's Linear Applications Handbook of 1994. The circuit can be implemented with equivalent operational. The detected voltage is given by the diode.
This circuit was published in a January 1971 issue of Radio Electronics to check television...
It is a circuit with the same characteristics as the previous one with the difference that it...
A load of up to 3 amps can be controlled by this circuit from a low current switch (reed-switch or other)...