In Old Movies, Why The Dial Tone After Someone Hangs Up?

Brace yourselves, we're about to get into some serious detail about telephone systems. Thanks to all the folks at Seattle's Museum of Communications! https://www.telcomhistory.org/connect... They're also on YouTube at    / museumofcomm   ...and Sarah has a personal blog specializing in the ongoing restoration of the 1923 Panel Switch at the Museum:   / revertive-pulse   Edited by Michelle Martin, @mrsmmartin I'm at http://tomscott.com on Twitter at   / tomscott   on Facebook at   / tomscott   and on Instagram and Snapchat as tomscottgo