relatively small screen size and the size of their keyboards. Typically, smartphones feature such tools as cameras, media players, web browsers, email clients, interactive maps, satellite navigation and a variety of sensors, such as a compass, accelerometers and GPS receivers. In addition to voice calls, smartphone users commonly communicate using a wide variety of messaging formats, including SMS, MMS, email, and various proprietary messaging services, such as iMessage and various social media platforms. Satellite phones A satellite telephone, or satphone, is a type of mobile phone that connects to other phones or the telephone network by radio link through satellites orbiting the Earth instead of terrestrial cell sites, as cellphones do. Therefore, they can work in most geographic locations on the Earth's surface, as long as open sky and the line-of-sight between the phone and the satellite is provided. Depending on the architecture of a particular system, coverage may include the entire Earth or only specific regions. Satellite phones provide similar functionality to terrestrial mobile telephones; voice calling, text messaging, and low-bandwidth Internet access are supported through most systems. The advantage of a satellite phone is that it can be used in such regions where local terrestrial communication infrastructures, such as landline and cellular networks, are not available. Satellite phones are popular on expeditions into remote locations, hunting, fishing, maritime sector, humanitarian missions, business trips, and mining in hard-to-reach areas, where there is no reliable cellular service. Satellite telephones rarely get disrupted by natural disasters on Earth or human actions such as war, so they have proven to be dependable communication tools in emergency situations, when the local communications system can be compromised. See also Bell System Bell Telephone Memorial Cellular network Cordless telephone Harvard sentences Index of telephone-related articles Jipp curve List of telephone operating companies Mobile operating system Multimedia messaging service (MMS) Party line (telephony) Phone hacking Radiotelephone Satellite phone SIM card Spamming Telephone keypad Telephone jack and plug Telephone tapping Tip and ring Videophone References Further reading Brooks, John (1976). Telephone: The first hundred years. HarperCollins. Casson, Herbert Newton. (1910) The history of the telephone online. Coe, Lewis (1995). The Telephone and Its Several Inventors: A History. Jefferson, NC: McFarland & Co. Evenson, A. Edward (2000). The Telephone Patent Conspiracy of 1876: The Elisha Gray – Alexander Bell Controversy. Jefferson, NC: McFarland & Co. Fischer, Claude S. (1994) America calling: A social history of the telephone to