Fax over IP (T.38)
Fax over IP (FoIP) carries fax transmissions over an internet or IP network instead of an analogue phone line, most reliably using the T.38 protocol.
How fax over IP works
Fax machines were built for analogue phone lines, which is why sending a fax over the internet needs care. There are two main methods:
- T.38 — a protocol designed for fax. It turns the fax into data packets and resends lost data, so it copes well with imperfect networks.
- G.711 pass-through — the fax tones are sent like a normal voice call with an uncompressed codec. It works on good connections but is more sensitive to packet loss.
Online fax services receive the fax and deliver it as a document, usually a PDF, by email.
Fax in phone.systems™
phone.systems™ receives faxes with the Fax object in a call flow. Connect it to a phone number and incoming faxes are delivered as PDF files through a delivery method, such as email or file storage. Both T.38 and G.711 pass-through are supported. Faxes also appear as attachments in the phone.systems™ app. phone.systems™ handles incoming faxes; sending faxes is not documented.