This sensor circuit for currents of the order of nanoamperes was found in an American documentation from the 1980s. The components are from that time.
February 25, 2015 - Mouser Electronics, Inc. today announced their new Robotics Technology site....
This circuit was found in an Australian publication from 1991. The circuit emits a tone as well as...
This circuit is from an old publication but can be implemented with modern silicon transistors such as...