This circuit was found in an American documentation from the 80's. The sensor is a special integrated circuit, uncommon in our times. There are modern equivalents.
This traditional circuit of old documentation uses a 0-1 mA milliammeter and has several scales....
This integrated amplifier was used in televisions from the 70s, with good sensitivity...
We find this efficient emergency lighting system in a 1987 publication. The circuit keeps a...