Sorry Stamp but I have to call this like I see it. RJ45 to DB9 adapter = lazy technician. I cannot tell you how many times I have had techs blame my code for a device not communicating only to find out that they grabbed an already terminated adapter off the van and it was pinned wrong. If you solder you will always get it right. If your engineering department or programmer haven't provided you with schematics for pin-outs on the DB9 connectors then they are not doing their job correctly. Our techs used those damned adapters on most of the jobs when I first started with the company. Even with pin-out schematics there would always be at least one problem with the wiring on every job. We work in the electronics field and yet I meet many people who cannot solder to save their lives. How is that possible? Learn to use a portable soldering iron, build a few soldering jigs for male and female connectors (with a custom made heatsink on the back so you dont melt the pins) and get the job done. It's cleaner and more professional looking in the long run.

There are many reasons NOT to use CAT cables for serial communications. The primary reason is the noise cancelling effect of the twisted pairs. Yeah yeah, you've never had a problem. Congrats on having an awesome streak of luck. Serial communications is limited in distance to 50' at 9600 Baud, by specification. The length drops with lower wire gauge, higher Baud rates and/or sheilded cable. Yes, sheilded cable actually shortens the length the signal can travel. I don't expect you to believe me but you might want to pick up a copy of Serial Port Complete by Jan Axelson for confirmation. Amazon usually has it available for not a lot of money. It is an in depth study of serial communications from spec standards to wire lengths to UART differences. It won't help you with the protocols but it will help you understand how serial communications works. The good news is that Belden sells actual cables designed for RS-232/RS-422 spec and other cables for RS-485 spec. The Belden 9533, 9535, 9537 and 9539 cables are what you would want to use. You will rarely use a 9539 except to make a full 9 conductor cable and the only reason to buy this cable is to make a 50' serial cable for loading processors from the comfort of the couch. The 9533 is going to be the most common cable you use as it is TX, RX and GND only. For stocking purposes you could keep the 9535 on hand at all times. This would cover 98% of your installs as it gives you TX, RX, GND, CTS, RTS.

I have seen many instances where the installers have only pulled a CAT5 cable for serial communications and it didnt work. The length was about 35 to 40 feet on each of those problem jobs. The units had to be switched to IR control and that sucked from my standpoint as I lost all real feedback from the device so all my time programming (and counting on that feedback) was wasted. It will happen at some point in your career and inevitably it will happen when you must have 2 way comm and cannot get a new wire there. Pull the right wire and you won't have that problem.

You might want to invest in a cable tester like this one:

[Link: google.com]