This is the circuit board. A bit of a giveway is the description "Econet Box Terminator", meaning that it's exactly the same board as for the socket boxes. The difference with the terminators is that the right-hand socket is removed, and five resistors and a capacitor are added in the spaces provided.

The terminator box can be used in the same way as a socket box, with an Econet station plugged into the available socket.