Comcast’s upcoming “TV Everywhere” online video service gained its first major broadcast network partner this week as CBS said Tuesday that it would join more than 20 cable networks in offering television shows through the trial service that is slated for launch in several weeks. Announced last month, Comcast’s online video initiative constitutes the first service of its kind to be offered by a cable operator and would provide viewers with the ability to access cable and broadcast network programs free-of-charge through their PCs and, potentially, through mobile devices. Streaming video would be offered exclusively to Comcast subscribers via two company websites—Comcast.net and Fancast.com—with tests of the on-demand service to encompass 5,000 customers. Although subscribers would receive programs at no additional charge, ads will be included in the service. In addition to CBS, seventeen cable networks also agreed to join the trial on Tuesday, including A&E, AMC, the Food Network, the Hallmark Channel, and E! Entertainment. Five other cable networks—HBO, Cinemax, TNT, TBS and Starz—confirmed plans to participate last month. As Comcast executive vice president Matt Bond commented that the addition of CBS and other new partners “highlights the industry’s growing interest to bring long-form content to consumers via a secure and easy-to-use online platform,” a CBS official proclaimed that his company “is very supportive of initiatives that help extend our content to new platforms in such a way that we gain new audiences and additional value for our advertisers.”