Lionel U30C Tower Com. Disp. Says More:

[Train-O]

To All Forum Members,

Chuck, I did as you said with the "AUX-1 and 2" keys, and when I depressed the "AUX-1" key and then the numeral "7" key the Tower Com. said;
  "Chessie three-three-twelve, please, standby."

Otherwise, as only stated in the 'Instruction Booklet', is to just depress the numeral "7" key and Tower Com. says;
  "Chessie three-three-twelve you are cleared outbound." 

There, may be other announcements, but I have to play around to find the correct combination.

Thank You,

Ralph