This circuit of the 80s makes use of an operational one of the time. It can be designed with modern operationals and must use a symmetrical power supply.
This circuit for the VHF band of analog TV was found in Motorola documentation from the 70s. The...
This 1989 circuit activates a protection relay if one or two phases are missing from a three-phase...
This circuit for telecommunications was found in a 1987 documentation. Connected to the...