)
This circuit was found in a 80’s Popular Electronics. It issues a warning signal with the signal of the old type printer with parallel port.
This circuit uses unusual operational amplifiers, but equivalents can be tried. FETs can also be...
This circuit was obtained in a 1991 publication. What it does is to amplify a signal with unit...
This small digital transmitter uses a 1 MHz crystal, or another nearby frequency, to produce a...