Hi Jeff,
You should ideally use a shielded cable, particularly if you are going any distance. The PSL connection is serial and is potentially susceptible to external interference.
I have used non shielded cables out of necessity a few times and not had issues with short runs, but you never know when a source of interference might present itself.
I would definitely recommend using a shielded cable and they are readily available.
Nigel
#Carbonite