METOX and BISCAY CROSS are for the same radar warning system,METOX was the FuMB-1 radar warning receiver and the BISCAY cross was its antenna.
The receiver was located in the radio room and operated by an additional petty officer added to the boat for this purpose. It was made by METOX-GRANDIN ( hence the name ) and operated on the frequency band of 1.3 to 2.6 meters. The offical name of this set was FuMB-1 ( funkmess-beobachtungs-gerät ).
The BISCAY CROSS was the FuMB-1 antenna and since it was rushed into service sometime around Aug 1942 there was no time to make a water tight and pressure proof antenna and the modifications to the boat ( drilling holes through the pressure hull for cables and wires etc. ) so the cross was made from 2 pieces of wood ( at first old packing crate material !, no joke )
with the antenna wires nailed to this frame. This cross had to be brought up to the bridge when on the surface and thrown dowh the hatch in a crash dive ! and in between when on the surface it had to be rotated by hand. Very hi-tech equipment here !!
If this receiver detected radar being used it would give an audible warning over the ships speaker sytem, the louder it was the closer the source of the detected radar was.