We found this circuit in the September 1971 issue of Radio Electronics magazine. The sensor is an LDR and R1 adjusts the sensitivity. A relay with the appropriate voltage can be used instead of a buzzer.
This circuit is from Mallory 1968 documentation. The circuit makes use of period components and...
This circuit can be applied to several logics. The circuit is from an Electronics Now from the...
In figures 1 and 2 we have two current drains that can be made with operational amplifiers and...