Econet
Test
Box
Econet
Test
Box
The Econet Test Box is intended to be connected to the user port of a Master 128 running the test software. Unfortunately I do not have the test software. I think it connects to the Master's Econet socket via the "Tester" socket on the front. The "UUT" socket is used to connect the box directly into a network via a socket box rather than into another machine.
The power connector is something of a puzzle as this is not mentioned in the FileStore Service Manual. Practically all devices connected to the BBC user port draw their power from there and the Econet Test Box seems to be no exception as it will happily provide a clock signal on the network once it is connected to the user port and an Econet socket box.