This circuit was suggested by Sprague Electric in an 80's documentation. The circuit uses a tachometric sensor for feedback. The current was not indicated in the original documentation.
Of course, other frequencies can be generated by changing the components. The circuit generates a...
This circuit was found in a 1974 publication. It provides a tone indication of the temperature sensed by...
This spy transmitter can be plugged directly into a power outlet. The power comes from a regulated...