This circuit was found in a 1992 publication. What it does is to light an external lamp when it gets dark. The trigger point adjustment is made in a potentiometer or trimpot and the sensor is a common LDR.
This circuit uses an optocoupler with a phototriac or optotriac to drive an external triac. The...
This circuit was published in an English magazine from 1980. The magazine no longer exists, but...
This mixer configuration from a 1967 publication can be adapted to work with modern transistors. The...