You can go to YouTube and watch PRR Publicity Film "Clear Track Ahead". HIGHLY recommend if you have never seen it! Anyhow shows Engineer Jim in the Cab of his T1 using Trainphone to talk to tower, other trains and the caboose and has an Animation explaining how it works!
Did NOT show him saying Clear The Track I intend to do 110 MPH gotta beat the Empire State Express. LOL
Had to use his name (easy to remember for me) - Jim