Found in 1980s Electronic Engineering, this circuit uses common phototransistors as sensors. The circuit is CMOS using an integrated 4011.
I found this circuit on a December 1976 Radio Elettronica. The Italian magazine no longer exists, but...
This circuit for the power grid was found in the June 1969 Radio Electronics magazine. The load is...
This circuit with common CMOS components was found in the November 1984 issue of Radio Electronics...