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Zoom Adds VoIP Support To DSL Modem

Zoom Technologies announced Monday (July 12) it has added voice-over-IP capabilities to a DSL modem architecture that also includes support for a PSTN connection.

Increasing interest in residential VoIP services has modem manufacturers and carriers rethinking the modem architectures deployed in broadband-enabled homes. To date, carriers have added VoIP capabilities by adding an analog telephone adapter (ATA) box to a home network in order to convert existing PSTN signals into VoIP streams carried over an IP network. To be cost effective, most carriers and modem manufacturers believe that the analog adapter must become an embedded element inside the DSL modem architecture.

"The addition of the ATA adds $20 in retail," said Terry Manning, Zoom's vice president of marketing. "But that cost is much less than adding a separate ATA."

Cost, however, isn't the only thing driving ATA integration. The external serial ATA also causes some technical difficulties in home networking designs. External boxes have had problems interacting with the network address translation (NAT) and firewall capabilities inherent in a DSL modem design, said Hume Vance, director of firmware engineering at Zoom.

To solve the problems, Zoom has opted to combine the ATA functions into its ADSL X5v modem design. The X5v combines an ADL modem powered by Conexant's silicon, a NAT firewall, a USB port and a four-port Ethernet switch. To add VoIP support, Zoom added an external VoIP processor which was also developed by Conexant. "Conexant was ahead in integrating VoIP into DSL," Hume said. He added that Zoom "has a lot of experience with Conexant's silicon."

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