Hi 422 can be an impedance controlled line with terminations. 232 tends to be under driven on typical lines and unterminated. This means that an 232 signal will look like a stair case to the receiver input that on long runs may cause intermittent edges. At lower baud rates, most 232 receivers can handle this much distortion. Also, since it is under driven, the signal can be corrupted by even a small amount of outside noise. This is made even worse because it is single ended and any common mode noise can corrupt the signal. In other words, just because you ran it in your house for 30 feet and never saw an error doesn't mean it can be done in all cases. 422 is impedance controlled and can be used at baud rates up to 5 or 10 MHz ( depending on manufacturer ). It can do this until resistive losses bring the level too low to be detected. Being differential, only common mode noise that pushed it beyond the common mode will be an issue and if the noise is short term, the receivers are designed to not switch the outputs until they are brought back into the common mode. I once designed a communications bus using RS-485 ( similar to RS-422 ) lines to interconnect several machines in a noisy environment. The previous design used RS-232 and was not robust enough to work in that same environment. The lines were less than 15 feet on the RS-232. The RS-485 setup ran for over 10 years without logging a single bit of data loss ( there were several component failures during that time that don't count ). Dwight drives) --------------------------------------------------------------------------