OG GarlicSalt

Probably not a PN change unless its part of a SB or AD, most probably a mod status change.

Both part numbers serve the same purposes and meet the same TCAS spec but the manufacturers and system are different the first pn is more of an all in one solution while the 2nd pn is part of the entire honeywell TCAS setup.

By no means an expert on this but I feel this should answer most of your question.