Half of Britain is said to be agog that a cell phone ringtone is the best-selling single this week. The other half is mystified or irritated. As for me, it’s further proof that those of us on the wrong side of the digital divide (generational division) must scramble to try to keep up. Confession: I’ve downloaded a ringtone or two on my cell, but returned to my retro ring from Bell days. On my desk, by the way, is a working Western Electric dial phone from 1935.