Why does a phone ring at the end of Bowie's "Life on Mars?"

Yesterday was the 50th anniversary of the single release of David Bowie's now-iconic Hunky Dory track, "Life on Mars?" If you've ever wondered if that phone ringing at the end of the track was intentional or not, here's producer Ken Scott explaining.

And, in honor of the 50th anniversary, here's the full version on Mick Rock's groundbreaking video with the phone ringing and Rono's cursing restored.