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 power supply was originally created for the CB16760E (Loudness System) but can be used in any...
Found in 1980s Electronic Engineering, this circuit uses common phototransistors as sensors. The...
This simple, unregulated power supply with an approximate 6 V output voltage can supply currents up to...