Even in these days of radio and satellite communications, the U.S. Navy uses the international alphabet flags, numeral pennants, numeral flags, and special flags and pennants for visual signaling. These signal flags are used to communicate while maintaining radio silence. Navy Signalmen transmit messages by hoisting a flag or a series of flags on a halyard. Each side of the ship has halyards and a “flag bag”, containing a full set of signal flags. Signals unique to the Navy are used when communicating with other U.S. Navy or allied forces. When communicating with all other vessels, the International Code of Signals is used. The code/answer pennant precedes all signals in international code.