This two-tube circuit, one being a double, was found in Radio Electronics magazine from July 1958. The distance to the microphone depends on noise and losses. The cable must be shielded.
This circuit was found in the May 1959 Radio Electronics magazine. Its purpose is to provide bias...
In the figure we have a circuit that fires from a positive pulse of short duration applied to its...
We found this alarm in a 1992 documentation. The circuit has several timings and the relay can...