Comcast’s long-awaited announcement today that it will aggressively pursue Voice over IP service is just the latest salvo in the cable industry’s steady attack on telephony services.

Comcast Chief Executive Brian Roberts will detail his company’s aggressive plans to deploy VoIP today at the 15th Annual Smith Barney Citigroup Entertainment, Media and Telecommunications Conference in Arizona, according to the Wall Street Journal.

Roberts told the newspaper that his company will market a VoIP service to 15 million homes by the end of this year and to virtually all 40 million of the households that it passes within 18 months. Comcast’s goal is to land eight million phone subscribers within five years, or 20% of the homes its systems pass.

Comcast’s service will not be of the cheap and dirty variety, costing $39.95 to customers who also buy cable TV and high-speed Internet access. The company has gone to some lengths to perfect its service before deployment, including developing features such as , integrated messaging, call waiting and operator assistance, as well as 911 emergency service. It also built in battery backups to keep phone service working when commercial power fails. In addition, Comcast executives told the WSJ that they are working on features such as videophone service and a service that whispers a caller’s identity.

According to In-Stat’s report, "Cable Telephony Service: VoIP Finally Shows Up", cable’s use of VoIP will steadily increase its presence in telephony, even though most cable telephony subscribers still rely on circuit-switched technology. As of late 2004, more than 11 million households and businesses worldwide have signed up for cable telephony service, according to Michael Paxton, senior analyst. Comcast continues to operate the circuit-switched voice business it inherited when it bought AT&T, but stopped expanding that service more than a year ago.

In-Stat is projecting a “steady rise” in worldwide VoIP subscribers, particularly over the next two years, as VoIP is more widely deployed.

It projects cable telephony subscribership of more than 14 million by late 2005, and more than 22 million by year-end 2008. Comcast is the last of the large cable entities to announce its VoIP push. Time Warner has already signed up 200,000 VoIP customers, according to the company. Cox Communications and Cablevision have also done voice deployments.