This circuit was obtained from an American documentation from the 1970s. Information on the current obtained and the winding of the transformer is not given.
Found in a Popular Electronics from the 90's, this circuit detects the approach of objects by the...
This old 4-channel circuit was found in the December 1994 Electronics Now magazine. The circuit uses...
The figure shows how to implement an alarm buzzer in an LM3914 to warn about crossing the scale...