mode c

[activewaypoint]

If one box is working on mode a only, the other is fully serviceable
fully mode s, c. Can you dispatch? Can't see it in the mel.

[Golden Rivet]

You can dispatch in this condition - you still have one fully serviceable Transponder.

A transponder with an altitude reporting capability( Mode C) is required for all flights in upper airspace, in controlled airspace above FL100, in special Rules Airspace and RVSM Airspace.

GR

edited for a bit of RTFQ