This circuit for AC loads was found in February 1976, Radio Electronics magazine. The triac is common, and the times are given by the 20 MΩ resistor and the 1 uF capacitor.
The sensor of this circuit can be any phototransistor and the SCR can be the TIC106. The circuit and...
We found this circuit in the Linear Applications Handbook of the National Semiconductor of 1994....
Using the well-known 2N2646 that was popular at the time, this circuit was found in Radio...