An urgent call is a type of communication used to alert people of an emergency situation. It can take the form of a PLEA, an all-points bulletin (APB), or a distress signal such as an SOS. A PLEA is a formal request for help or mercy, while an APB is a broadcast issued by law enforcement agencies to enlist the public's help in locating a person or vehicle. An SOS is an internationally recognized distress signal used to indicate a life-threatening situation.