Published by Philips in 1965 documentation, the sensor for this circuit is a common LDR. The transistors are general-purpose types from the time, only TR3 is a power type according to the load.
This circuit was found in a 1980s Intersil documentation. The integrated circuit used is not...
Although it is a common configuration today, these circuits were taken from an old publication. The...
This circuit, from an old publication, can also use modern transistors. Note that the unit is...