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VoIP Voice and Fax Signal Processing by Sivannarayana Nagireddi

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15.8 MIGRATING MODEM FUNCTIONS TO IP

A telephone is used along with a VoIP adapter and gateways for voice communication on IP. A fax may also use the same telephone interface of the adapter. A dial-up modem was used on telephone lines along with a computer for Internet connectivity. The use of a modem through the same telephone interfaces of the VoIP system is also possible. The modem is usually part of a PC or laptop or is external to the computer. The modem inside the computer will have a telephone interface. An external modem will have a computer interface for data connectivity on the one side and a telephone interface on the other side. VoIP adapters and integrated access devices (IADs) will have multiple interfaces for broadband connectivity as given in Chapter 2. Internet connectivity is extended directly through broadband interfaces instead of a modem. Dial-up modem connectivity through a telephone interface has limited use in VoIP adapters and gateways. Hence, modem connectivity through a dial-up modem did not gain much popularity. In the following sections, an overview on modem connectivity for migrating the PSTN to VoIP infrastructure is given. While writing this section, the end users were not using MoIP service.

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Figure 15.5. Functional PSTN setup to connect the PC modem for Internet connectivity.

15.8.1 Modem Simple Connectivity Through an FXO

Some VoIP IADs has digital ...

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