This circuit is from a 1964 Electronic Design. The sensor is an LDR and the transistors are general-purpose types. The circuit triggers when the light that falls on the sensor is cut off.
This circuit was obtained in an 1975 English publication. It is a voltage regulator circuit for...
In the figure we have an infrared receiver circuit using an operational 741. The circuit is an...
This circuit is suggested by National Semiconductor and makes use of the negative regulator LM2990...