On the A330 there are 3 sets of downlock proximity sensors on each gear, LGCIU 1+2 and an independent system.
If LGCIU 1+2 fail you will still get the Landing Gear lights on the centre instrument panel from the independent sensors which operate via LGCIU 1 ( yes even if LGCIU 1 is broken and de-powered the independent still works )
I would think the 320 would be similar.
Last edited by nitpicker330; 9th July 2012 at 11:29.