It doesn't make sense to me, but I don't claim to be an expert on the topic. I suspect if you could point us to a "digital fax" we could point you at a "digital modem" that worked with the accuvote.
That said, I think people should be pretty careful with this topic unless they really do think they know what they are talking about. There is no such thing as a "digital modem" -- that is an oxymoron. Telephones (the things with the keypad and handset) are analogue equipment, period, even if the guy who installed the phones in the schools told them otherwise.