It is expensive but it works. It's industrial grade electronics so it's designed to be immune to electrical noise and disturbances created by other electrical and electronic equipment (which also includes alternators, starter motors, wiper motors and ignition circuits which are very noisy equipment due to their nature). It's also very fast and stable. I had no end of trouble with the cheap £15/£20 ones and then used one of these units then promptly never used another one again. I use it day in day out and have done with increasing frequency since 2003/4 and it's never let me down connecting to a varying array of devices. Back then it was "only" £125!

If you can find something cheaper that will do the job you need it to then fair play. If anyone ever asks about RS232 converters I always recommend this item as it simply works which I can't say for any of the cheap versions I have used. It works on XP, Vista and Windows & too.