This resistive sensor was found in a 1969 US documentation. The circuit uses transistors of the time, but current equivalents can be employed.
The sensors of this liquid alarm are formed by two pieces of wire with the ends peeled off. The...
The three-input audio mixer or mixer shown in the figure was suggested by the Linear Applications Handbook...
In the figure we have a classic Clapp oscillator configuration for a frequency of a few tens of...