Has anyone ever tried to interface a Pelco CCTV keyboard to Mach? This seems like it wouldd be perfect as a pendant controller. It speaks ASCII, uses RS422 (and RS232 I think) interfacing, and it's pretty well documented. Model is KBD300A
They show up on ebay often and are in heavy use in CCTV.
Spec sheet here: ftp://www.pelco.com/ProductSpecs/c527.PDF