We found this circuit in an Electronics Now from the 1990s. The circuit crashes when light strikes the sensor. Instead of the alarm a relay can be used to drive higher power devices.
This electromyography monitor is from a 1978 publication on operational amplifiers. The components are...
Found in a 2005 Linear Technology application manual, this circuit monitors the current in a load...
This circuit was found in a Popular Electronics from the 90's. The power transistors must be...