This circuit was found in 1960s Radio Electronics. The circuit uses components from that time. The triac is according to the controlled load. The sensor is a common LDR.
We found this circuit in an American publication from 1977. Operationals can be type 741 with...
Found in an American 1980s documentation, this circuit makes use of a sensor of the era uncommon...
This somewhat unusual configuration, mainly in the form of adjustment, is from a 1978 publication. The...