VoIP Voice and Fax Signal Processing

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FAX OVER IP AND MODEM OVER IP

The fax over IP (FoIP) application enables standard fax machines to work with VoIP infrastructure. The voice interfaces on VoIP customer premises equipment (CPE)—also called the VoIP adapter or gateway—can support fax calls much the same way public switched telephone network (PSTN) telephone interfaces support them. The two most popular methods to send fax over IP networks are store-and-forward fax service and real-time fax over IP. The main difference between the real time and store-and-forward approach is the delivery and method of reception confirmation. This chapter describes the VoIP fax, Session Initiation Protocol (SIP) based T.38 fax call, fax pass-through, fax over IP testing, and interoperability issues in fax over IP. The modem over IP (MoIP) is presented at a high level as an introduction to this topic.