Found in a 90's EDN this circuit can be used as a shield. The transistor is a general-purpose type and the frequency of the emitted sound is determined by R1 / C1.
This 12V battery charging circuit automatically shuts off at the end of the charge. The disconnect...
We do not know exactly what sound a flying saucer makes, or if it makes a sound! But this is not...
This simple 1 transistor circuit was found in an American documentation from the 60's. The...