This Linear Technology circuit can measure currents from 100 pA to 100 uA. The circuit is from the 80's, using a component of the era. Transistors are general purpose types.
This alarm, found in a 2002 documentation, uses several sensors and has a 12 V supply, not...
This circuit uses a special 1950's RCA strobe tube. It can be built with equivalent components for the rest...
This circuit, which can act as a shield, was found in a 1970s American documentation. The...