Found in a 90’s Electronics Now, this circuit has its output connected to an audio amplifier. The transducer is the type that fits on the finger to monitor the transparency and thus the beats.
We found this circuit in a 1968 Electronics World. The circuit uses a transistor of the time...
This simple humidity sensor can be used in rain or leak detectors. The circuit is for 12 V supply,...
The circuit shown in the figure is recommended for applications where a visual indication is...