This circuit is based on the light comparison of two LDR sensors. We found it in a 90s Popular Electronics. The transistor must be according to the indicator or load being driven.
Capacitor C and resistor R in this circuit determine the time the output remains at the high level...
We found this circuit in the Linear Applications Handbook of the 1994 National Semiconductor. The...
The transistors in this circuit from a 1994 technical publication may be BC548 and the 12 V supply...