The two chips form a complete voice solution that can be added to next-generation DSL and cable modems, network interface devices, set-top boxes, broadband wireless receivers and home routers, said Angela Raucher, product-marketing manager for broadband communications at Texas Instruments.

The TI-Intersil solution is agnostic, providing POTS (plain old telephone service) independently of the broadband medium — cable, digital subscriber lines, T1 lines or wireless links, she said.

The TI quad-channel codec, the TP2450, is impedance-matched with Intersil's ISL5587 dual-channel SLIC. Both chips operate from a single 3.3-volt power supply for line-powered applications. The TI codec is priced at $7 to $8, depending on volumes, and the Intersil SLIC costs $5 to $6.

Voice-over-cable module

In a separate effort, TI has dedicated a fairly large engineering team to a customer-specific, two-chip module that supports voice-over-cable, said Joe Nabicht, who headed up the design effort. Nabicht described the module at the recent Custom Integrated Circuits Conference in Orlando, Fla.

The TP2450 codec is designed to support existing silicon — such as a communications processor — in a cable modem.By contrast, the two-chip cable telephony module combines all of the functions — except for a high-voltage SLIC — needed to provide four phone lines within a home or office, including the codec, communications processor, and some customer-specific functions.

The customer, which TI declined to identify, will combine the module with a SLIC to provide a customer-premise device used in homes or small offices. Nabicht said the module houses a small digital ASIC built around an ARM7 processor core. The larger second chip is a mixed-signal ASIC with a baseband data processor on board to handle communications with the cable head-end, and which acts as a slave processor to the ARM microcontroller.

Nabicht said in the next iteration, TI may move the mixed-signal functions to a digital ASIC, providing a single-chip solution.

Will Strauss, president of market research firm Forward Concepts, said that for the voice-over-broadband (VoB) market to take off, integration efforts — such as those at TI and Intersil — need to be applied to reduce the bill of materials. Beyond the engineering work, service providers must make the needed infrastructure investments.

In the United States, where circuit-switched voice must be able to operate through thunderstorms and other power outages, VoB acceptance has been muted, Strauss said.

On the DSL front, telecom companies are keeping investments in new technology to a minimum. Despite predictions that cable service providers will mount major voice-service challenges to the traditional voice telecom providers, Strauss argued that most of the U.S. cable providers are "risk-averse. They are cheap when it comes to new investments, unless there is a guaranteed return."

U.S. cable providers have organized a number of field trials for voice-over-cable, but Strauss said that overall, "voice-over-cable has gone over like a lead balloon in the United States. In countries that have a less well-developed infrastructure, such as Brazil or China, voice-over-cable has been more of a barn burner."

One reason is that the high-level protocols needed to support voice-over-cable are not quite mature, Strauss said, noting that the Docsis 1.1 standard that supports an acceptable quality of service has only been in place for a few months.

Various market research firms have differing ways of looking at the VoB market, tracking boxes with voice capability, the number of paying subscribers and voice-capable installed networks. Nevertheless, the major market watchers all foresee strong growth over the next few years, albeit from a small base.

Forward Concepts predicts that the VoB customer premises equipment market will grow at a 74 percent compound annual growth rate over a five-year period, to more than 27 million ports shipped in 2006. Strauss said much of that equipment will be voice-over-packet telephony systems used in offices that have Internet Protocol PBXs, adding that the IP PBX market grew by 130 percent last year.

In-Stat/MDR is predicting that voice-over-cable will grow from 4.6 million paying subscribers worldwide last year to 15 million by 2005. Those subscribers will be paying for a suite of services, including multiple phone lines, cable TV and high-speed data, adding to the total revenue opportunity.