This is what the insides look like.

The yellow square is the digital logic board. It contains the GPIB circuits, the microcontroller and the EEPROMS which store the software.

The blue section is the power supply section which generate the multiple power rails.

The red section is the relay card with its eight high-speed high-voltage relays.

Lastly on the bottom we have the RFI/EMI shield. This shield protects the sensitive circuits from the effects of stray radiation.