Land mobile radio system (LMRS), also called public land mobile radio or private land mobile radio, is a wireless communications system intended for use by terrestrial users in vehicles (mobiles) or on foot (portables). Examples are walkie-talkies and two way radios in vehicles. Such systems are used by emergency first responder organizations such as police, fire, and ambulance services, public works organizations, dispatched services such as taxis, or companies with large vehicle fleets or numerous field staff. Such a system can be independent, but often can be connected to other fixed systems such as the public switched telephone network (PSTN) or cellular networks.