Raytheon's used integrated circuit is no longer common today. The circuit was obtained in a documentation from the 80's and must be powered by a symmetrical source.
This circuit, suggested by Signetics can be used as a shield. Modern operational can be employed...
In the figure we have a typical voltage follower. In a voltage follower the voltage gain is...
This 2001 circuit uses common transistors and can be used in an electronic lock. The relay trips...