Modems with Embedded Multimedia Terminal Adapters are cable modems with an analog-to-digital telephone adapter integrated with the modem's cable network access hardware. This allows the cable modem to utilize analog phones with a cable provider's Voice Over IP services.
Traditional telephone lines use an analog communication infrastructure to transmit voice calls that was also utilized by older telephone modem systems to transmit digital data between computers as sound signals. High-speed cable Internet networks are now capable of transmitting voice data digitally through VoIP technologies, inverting the relationship of phone modems and analog telephone lines by delivering the equivalent of traditional telephone services over a digital data connection.
Traditional phone equipment still produces and receives analog signals, so it is necessary to convert the outgoing analog signal from the phone to a digital signal for use over data networks. This conversion is accomplished via the EMTA adapter incorporated in many cable modems. The EMTA in a cable modem is also responsible for converting the incoming digital voice data from a VoIP connection back to an analog signal for an attached phone, as well as providing ring and dial tone signals. EMTA adapters are also used in the equipment offered by telephone providers such as MagicJack and Vonage, in addition to cable modems that accomplish the same function.