This busy line indicator is very simple, serving for analog lines. The supply is made by two batteries and the transistors admit equivalents.
This circuit is from the 1993 Motorola Linear Interface ICs. Equivalent operating may be used and...
Through the TTL output this circuit can be used as a shield. The sensor is a platinum probe, and...
This alarm with sensors in series and parallel was found in the 1995 Encyclopedia of Electronic...