Cox Communications is using a "hybrid" switch from Nortel Networks to migrate its existing circuit-switched telephony markets to a platform based on IP technology.

Nortel's hybrid switch, perhaps best described as the "Prius" of the VoIP world, is an IP softswitch that also leverages the service operator's existing circuit-switched infrastructure.

Using a Nortel CS 2000 softswitch outfitted with a special core processor and software load and with the addition of a gateway controller, operators can run IP and traditional circuit-switched voice services in the market, with the goal of eventually moving everything over to IP.

"Cox or any other company...can fully migrate or evolve to the IP side of the switch," explained Elaine Smiles, Nortel's director of cable marketing.

Initially, Cox will tap the media gateway function of Nortel's hybrid switch. Later on, if Cox decides to launch remote sites off that hybrid switch, it could employ media gateways from Nuera Communications - one of Nortel's technology partners.

Cox and Nortel revealed additional details about the plan and the approach in a recently released whitepaper.

In addition to taking advantage of IP technology, using the hybrid approach in existing circuit-switched markets will also enable Cox to use its existing infrastructure of rate centers, SS7 links, and to use the same switch to supply E911 and CALEA support.

Cox will stop installing traditional NIUs in existing circuit-switched voice markets once a hybrid switch is installed, noted Jay Rolls, Cox's vice president of telephony and data engineering.

Cox is already in the process of deploying the Nortel hybrid in some markets. Under the agreement with Nortel, Cox is committed to upgrading at least 10 Nortel DMS switches with hybrid softswitch capabilities.

Cox currently uses circuit-switched technology in markets such as Orange County and San Diego, Calif.; Phoenix and Tucson, Ariz.; Omaha, Neb.; Hartford, Conn.; Rhode Island; Hampton Roads and Fairfax County, Va.; New Orleans, La.; Oklahoma City, Okla.; and Wichita, Kan. Cox has deployed softswitches to support residential and commercial voice customers in Roanoke, Va.; Tulsa, Okla.; Baton Rouge, La.; Lafayette/Southwest Louisiana; and five cities in West Texas.

Cox has 1.2 million telephony subs, but does not yet break out how many are of the VoIP variety. The company expects more than 50 percent of its new voice lines to be IP by the end of 2005.

Other operators that use Nortel's DMS switch for traditional telephony services could also employ the hybrid upgrade as part of a plan to migrate to VoIP. Telenet of Belgium, for example, has operated hybrid switches since last year.

Smiles estimates that Nortel presently has 150 DMSs in the field with MSOs such as NTL and Telewest in the United Kingdom, TeleCable in Spain, ETR in Chile, J-COM in Japan, and UnitedGlobalCom.