Aside from fax machines, there are many other kinds of modem devices on the telephone network.

  • Fire alarms
  • Credit card terminals
  • ATMs
  • Dial-up modems
  • Many more...


Modem-based devices manufactured today that would have been equipped with a phone modem in previous years often come equipped with a cell modem. Many of these no longer place voice calls to transfer data, instead using 3G. That said, there are still many legacy devices out there using modems connected to phone lines, or devices in areas with poor cell reception.


The T.38 protocol only supports fax modems, so these other types of modems do not receive the same protection from adverse network conditions as a fax machine. There is no open standard for transporting non-fax modems over the internet more reliably than with a standard VoIP call. That said, you're more than welcome to use a non-fax modem on our service. The ATA jitter buffer adjustments in our installation guides also help most modems, and we do support RFC2833 for transporting DTMF signals, which some modems use. Due to the diversity and highly proprietary nature of modems in use, we won't be able to debug the modem or the protocols it uses.