GPIB is the abbreviation of General Purpose Interface Bus. One of the earliest GPIB realizations
was the HPIB of Hewlett Packard in the early 60th. The GPIB is also known as IEC 625 or IEEE 488.
It is designed to connect test instruments for laboratory use into network.
Hence, the GPIB is very common to be used in EMC testing.
Of course, it is possible to link other test instruments into the EMC test system via GPIB, such as a volt meter
or an oscilloscope for EUT monitoring.
It is also possible to link another computer into the EMC test system. This could be good for separating the RF field control and the EUT monitoring. (A possible solution, if the EUT monitoring software is DOS-based, and that software cannot be ported into a Windows environment.)