MT75 Speedo wiring?

[magpies]

Hi
I've installed an MT75 box in my TVR (along with a cosy BOA). my old box was mechanical drive so I have bought a new programmable Speedo. There are three wired coming from the box to a triangular connector with Black, yellow and brown wires. I would think the black is earth and the other two are +12v and output signal - if this is correct is the brown the +12v and the yellow the signal to the speedo? or is there another way?

[S0 What]

Black is usually IGN live on fords and brown earth.

[magpies]

cheers

- yep Brown = earth, black +12v and yellow signal to speedo