19-03-2015, 05:43 PM
That's the transponder unit for the key chip on the IR systems which have a separate Alarm & CL control unit elsewhere, RF system has an integrated Alarm ECU & transponder unit which is the one with two plugs that people mistakenly call a BSI.
need a part number? http://public.servicebox.peugeot.com/ and http://service.citroen.com/ will sort you out.