As aircraft operating in airspace occupied by other aircraft, hang glider pilots also use the appropriate type of radio (i.e. the aircraft transceiver into Aero Mobile Service VHF band). It can, of course, be fitted with a PTT switch to a finger and speakers inside the helmet. The use of aircraft transceivers is subject to regulations specific to the use in the air such as frequencies restrictions, but has several advantages over FM (i.e. frequency modulated) radios used in other services. First is the great range it has (without repeaters) because of its amplitude modulation (i.e. AM). Second is the ability to contact, inform and be informed directly by other aircraft pilots of their intentions thereby improving collision avoidance and increasing safety. Third is to allow greater liberty regarding distance flights in regulated airspaces, in which the aircraft radio is normally a legal requirement. Fourth is the universal emergency frequency monitored by all other users and satellites and used in case of emergency or impending emergency.