An interesting post has appeared on line about the new phone systems in use aboard Air Force One. It's an interesting read:
http://electrospaces.blogspot.com/2014/07/new-phones-aboard-air-force-one.html
There is also an story on something I've always wondered about, how they got a secured Blackberry for President Obama:
http://electrospaces.blogspot.com/2013/04/how-obamas-blackberry-got-secured.html