The satellite phone is a briefcase-shaped device with its flap serving as an antennae.  Unlike a mobile phone, a satellite phone is independent of land links and is hooked onto a network of satellites covering the globe.

A satellite phone is a special kind of mobile phone that is designed to permit voice and data transmission via satellite.  If you work, live or travel in areas outside cellular coverage or in areas within adequate landline service, a satellite phone is for you.

The wireless satellite phone is enabled by GMSS (Geostationary Mobile Satellite Standard), the satellite technology derived from the GSM standard. 

Journalists, people in the military, and politicians who travel the globe all know the advantages of having a satellite phone.  With one of these devices you are able to communicate with anyone with a phone number from almost anywhere.

Although the satellite phone has made great strides in the past few years, the sat phone more closely resembles your portable home phone or one of those clunky cell phones from fifteen years ago.

Although you can call or receive calls in the middle of nowhere with a satellite phone, there are downsides.  Most phones need a clear "line of sight" to the satellite.  An errant cloud or two may not affect your phone transmission but a solar flare might.  The phones can come with extension cords connecting the phone to the antenna, allowing the antenna to be outside and you to be inside, making the call.

Another downside of the satellite phone is the limitations of bandwidth.  Some satellite phones use a narrow band, sending along your audio signal, but they cannot handle the high bandwidth information at near the speeds you find at home.  This means that you can have internet access, but for these phones that access is slow.

Satellite phone technology is advancing every day, so look for newer and better options for the world traveler.  Like cell phone companies, the satellite service provider often offers phones as well as the service in a neat little package.  If you don't intend to hook it up to a computer to send data and don't need to talk for long, then there is no need for the latest word in satellite phones.  Three major satellite phone networks are currently in operation: Iridium, Globalstar and Thuraya.

The use of low earth orbit satellites helps minimize round-trip-time, which greatly improves the perceived quality of the phone call.  Satellite phone calls are routed directly from one handheld unit to another, or to a terrestrial network.

A satellite phone rental gives you an opportunity to go anywhere with the confidence of knowing there is a phone you can use, and spare yourself the embarrassment of begging to use the only phone for miles or trying to find a payphone in some remote location.

Iridium is a profitable company and has been since 2004.  For a company like Iridium, whose satellite network services run 24 hours a day, 365 days a year, non-disruptive data migration is essential.  The company is focusing on specialized users: the military, the news media and the maritime industry.

The company's name comes from the platinum metal with atomic number 77 in the periodic table of elements, a reference to the initial plan to place 77 satellites in space.

Iridium delivers reliable, secure, real-time, mission-critical communications services to and from areas where landlines and terrestrial-based wireless services are either unavailable or unreliable.  Iridium is a mobile satellite service that provides ubiquitous, gap-free, reliable coverage over Polar Regions, which are used by aircraft on international flights. 

Iridium’s constellation of 66 low-earth-orbiting (LEO), cross-linked satellites (and multiple in-orbit spares) provides critical voice and data services for regions not served by other communication networks.  In addition to providing voice service, Iridium is marketing data communications for shipping companies that want to remotely monitor containers in transit.  They're targeting a much broader market of average business people and vertical markets like maritime, mining, forestry-people who operate in remote locations and they don't have access to cell, or in some cases, any phone service. 

Its 66 satellites provide 100% coverage of the globe, enabling callers to talk from high peaks or the middle of the high seas, and from practically anywhere in a largely unwired Third World.  To provide uninterrupted coverage around the globe, Iridium operators choreograph an intricate dance in space, monitoring the satellites as they speed along at 17,500 mph in crisscrossing paths 480 miles above Earth's surface. 

Their network support a variety of satellite phones. You can view some of them at

http://www.iridium.com/products/product.htm

Globalstar is a leading provider of global mobile satellite telecommunications services, offering both voice and data services from virtually anywhere in over 110 countries around the world.  The Globalstar is less expensive to purchase and operate than the Iridium and Inmarsat phones.

Globalstar's technology relies on a constellation of 48 satellites which connects with local wireline and cellular service providers to offer communications service virtually anywhere in the world.  They will meet the needs of cellular users and global travelers who roam outside of cellular coverage areas, as well as residents of under-served markets who will use Globalstar's fixed-site phones to satisfy their needs for basic telephony.

The company uses regional gateways to route calls from the satellite network to the destination phone number.  Their satellite constellation was repositioned in the period between mid-October 2006 and February 2007 in preparation for the expected insertion of 8 additional first generation satellites sometime in 2007 to replace satellites that have degraded.  Globalstar also stated that their expectation is that: “With the successful launch of eight new (first generation) satellites scheduled for this year, along with our existing satellite network, Globalstar will continue to provide and support two-way voice and data satellite services to our customers through the launch of the second-generation constellation”. 

Globalstar phones are capable of making calls in most weather conditions.  Globalstar's mobile satellite phones, only slightly larger than traditional cellular phones, are built by three of the world's top wireless manufacturers, Ericsson, QUALCOMM and Telit.

Globalstar offers an array of products and satellite phone services, designed to support almost any data or voice communications application wherever you live, travel or work.

Globalstar satellite phones function as both cellular and satellite phones providing service in many areas where cellular and landlines may never be able to go.  Globalstar automatically searches for a connection to the more cost-efficient analog or digital CDMA cellular networks.

As said before, Globalstar mobile phones function as both cellular and satellite phones providing service in areas where many cellular and landlines may never go.  They offer both voice and data services from virtually anywhere in over 110 countries around the world and they have an established network of over 340 distribution locations across North America, featuring a combination of wireless carrier outlets, satellite and two-way radio specialty communications dealers, and distributors with a specific vertical market focus.

Globalstar service is a satellite radio technology subject to transmission limitations caused by type of terrain, service area limits, customer equipment use and other variable conditions including the functionality and orbital locations of the satellites themselves.

The fixed satellite phones use Qualcomm's Code Division Multiple Access (CDMA) technology to operate on the Globalstar satellite communications system.  The fixed satellite telephone is an affordable solution, providing subscribers with a versatile and dependable phone for anywhere, anytime global communications.  Globalstar will meet the needs of cellular users and global travelers who roam outside of cellular coverage areas, as well as residents of under-served markets who will use Globalstar's fixed-site phones to satisfy their needs for basic telephony.

Satellite phones tend to be larger than cell phones and drop more calls.  On the other hand, Globalstar satellite phones can provide communication services from remote locations where cellular service is not available.  If cellular service is available where you're going, there probably is no reason to have a satellite phone.

Your Globalstar phone must maintain a direct line of sight with at least one satellite in order to make a call.  Globalstar phones are capable of making calls in most weather conditions.  By default, your Globalstar phone tries to use the strongest signal available to it.  It is the customer's responsibility to notice if his or her Globalstar phone has switched to a roaming service as indicated on the LCD screen of the phone.  If the phone is positioned on a black surface (such as asphalt) in direct strong sunlight, the temperature near the surface can be remarkably hot.

Some of their satellite phones are presented at this place:

Globalstar phones