Suggested by an American publication of 1964 this circuit is intended for the capture of signals from film tracks recorded by optical systems, common at the time.
This circuit is from an English publication from 1976 but can be easily assembled with BC548...
This configuration, found in many publications, is from an American book from 1981. The power...
The purpose of this circuit is to ensure that an auxiliary 12 V battery continues to supply power...