We found this circuit in a technical documentation for the National Semiconductor LM3909. The circuit consists of a low consumption continuity tester powered by a single battery.
This circuit is based on an uncommon Texas component today, as found in an American 1980s...
Despite being from a 1970 General Electric documentation this circuit can be used as a shield if...
This receiver was found in a 1968 publication, but can be mounted with a BC548 and BC558 in place...