Photometer for enlarger (CB8342E)

This circuit for old photo enlargers was found in a 1970s RCA manual. The components are from the time, but modern equivalents can be used.

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1 mA current drain (CB8850E)
This circuit was found in 90s Radio Electronics. The transistor can be any general purpose....
Monostable 4013 (CB11123E)
The circuit below shows how to obtain a monostable from a CMOS 4013 flip-flop. The actuation time...
Drift compensation for transducer (CB7367E)
This circuit is from Philips' 60s documentation. The circuit can be applied to modern operational...