This circuit is from a 1964 Electronic Design. The sensor is an LDR and the transistors are general-purpose types. The circuit triggers when the light that falls on the sensor is cut off.
We found this circuit in an American documentation from the 60's. The transistors are made of...
The accuracy of this circuit depends on adjustments made with capacitors of small tolerances of known...
The figure shows how to implement an OR function with two inputs, using a relay. The relay...