call sign

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun broadcasting A combination of letters and numbers used to identify a radio or television station.
• noun military Any combination of characters or pronounceable words, which identifies a communication facility, a command, an authority, an activity, or a unit; used primarily for establishing and maintaining communications. Also called CS. (JP 1-02 Department of Defense Dictionary of Military and Associated Terms.)