Using an LDR, this Philips circuit directly activates a relay when light strikes the sensor. The relay is 45 V with 20k coil resistance. The 220 nF capacitor must be polyester for 400 V.
Indicated by Popular Electronics to be used with a car headlight, this circuit can also have...
In this circuit of a 1970s publication, data from the coil to oscillate at the desired frequency...
This circuit was obtained from a Philips documentation from 1968. The transistors can be replaced...