Re: coax cable
Tom, coax is used for a great many things. Delkis is asking about coax used in computer networks (RG/58 thinet). 820 wouldn't be applicable there but that really doesn't matter. My point above is that all LV cables share the same system to determine uses. Once you know how that works you will be able to determine what cable, be it coax, twisted pair CAT5e or 18/2 thermostat, needs to be used for a particular application. For instance, if you are running a cable thorough a plenum or environmental air handling space you will know that whatever cable you use will have to have a "P" (for plenum) as the last letter in the cable type. (CATVP, CMP, CL2P, CL3P, FPLP, MPP, etc.)
If for some reason you don't have a plenum listed cable you can use a "lesser rated" one such as "R" (riser) or one with no designation if it's run in raceway or conduit.