A satellite telephone is nothing but a type of cell phone that, unlike any conventional mobile phone, provides service almost anywhere. It's usually more expensive than cell phones as they provide an important capability of receiving and making telephone calls at any time and from anywhere, independent of a local cell phone service or geographical boundaries.
A satellite telephone connects to a satellite in orbit for achieving communication. This is different from a conventional mobile phone that connects to a local and land-based service tower. Though cell phone networks use satellites for achieving a larger communication radius, mobile phones don't directly dial to these satellites.
Several satellite telephone networks use an interconnected network of satellites in the geosynchronous orbit that enables the network to attain global coverage with only three to four satellites. The other method of satellite telephone communication is to place the satellites in the low-earth orbit. This, however, requires more number of satellites for achieving global coverage. They can be smaller nevertheless for reducing launch costs.
The microwave transceiver of a satellite phone gives notoriously poor service indoors. In this regard, their reliability and performance is worse than a cell phone. Moreover, the networks that depend upon geosynchronous satellites usually suffer from a transmission delay of over a second. This is because satellites are positioned at about 23,000 miles in space. This means that every signal has to travel approximately 46,000 miles from one handset to the other. Besides, a satellite phone handset is more expensive than a mobile phone. In fact, both the handset and the service are priced much higher than conventional cell phones. Calling satellite phones from landlines or mobile phones is also very expensive although this hardly costs anything to the satellite phone owner. Satellite phones, however, should be the preferred device if you want reliable communication in remote areas where cell phone networks are weak.
A satellite phone is usually assigned its own special country code. For instance, Inmarsat phones are typically assigned the country codes between 870 and 874, while Iridium phones use the country codes 8816 and 8817.
The first satellite phone company of the world commenced its services in 1979, by the name of International Mobile Satellite Organization, a non-profit international body started by the United Nations. The service was started to provide a reliable channel for communication to the maritime community. From the very beginning, the organization was christened as Inmarsat which became a private company from 1999.
A notable problem with most satellite phones is that unlike cell phones, their networks usually operate near their full capacity even under normal circumstances. The networks usually don't have any extra capacity to accommodate more number of calls simultaneously. This means that any spike in the volume of calls, as has been the case during major regional and international disturbances, can cause a satellite phone network to collapse. Technological advancements, however, are being carried out so that satellite phone networks can get rid of these problems.