This interesting circuit uses a sodion valve that we have already described in an article on the website. The circuit uses several batteries for power. The phone is of high impedance.
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...