Just take a peek in your network closet, look at the power supply for your network switch or router, dont accidentally unplug your office network, do you see anything that says class 2 on it?
That would be a art 725.121 (A)(2) class 2 power supply.
A communications circuit as defined by article 800, I think of like 'service conductors' they originate from a provider, enter the building then go to all the customer owned equipment such as old landline phone, fax, T1 or DSL modems, stopping when that equipment powers a new circuit off local power.
Or the coax/fiber from the street to the first modem.
Like I said they make cat 5 and even cat 6 that is crush resistant and for any AHJ I know meets the 'barrier' requirement in 725.136(B)
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