CBS Broadcast Group President Howard Stringer quit the network today to head a new interactive media endeavor for a trio of phone companies. TIME correspondent Adam Cohen says the move "widely expected" because the anticipated sale of CBS most likely will spark a management shakeup. Stringer will run a Bell Atlantic, NYNEX and Pacific Telesis Group venture, with plans to begin delivery of an interactive information and home entertainment service through telephone lines -- including "video-on-demand" -- to more than 30 million homes by late 1995. Stringer, 53, who first distinguished himself as an Emmy-winning producer and president for CBS News, was credited with wooing David Letterman from NBC to give CBS its first-ever dominance in late-night, although the network has fallen to number three in overall ratings. CBS executive Peter Lund was named Stringer's replacement.