B&G_Focus_Speedsounder

[COCOLETRES]

I bought a 1992 Fairline 36 Brava which has a B&G Focus Speedsounder. It does not turn on, and I think it might just be a power supply problem.
It has two connections boxes, each one with three connectors. There are two control panel, one in the fly and the other one inside.
Can anybody tell me where the 12 VDC should be connected?
Thanks.
René.