Quad-band and tri-band are types of mobile phone technology. The essential difference between quad-band and tri-band phones is their likelihood to operate in different countries. Generally, tri-band phones will work in some countries, and quad-band phones will work in almost all countries. The terms quad-band and tri-band refer to the frequency bands that the phones will respond to in a mobile phone signal. These phones are used by travelers to areas in which a more limited, dual-band phone will no longer work.
Though both phones connect to multiple frequency bands, quad-band phones work in more areas. Tri-band supports connection to three bands of global system model (GSM) frequency, while quad-band supports four frequencies. Though the manufacturer generally advertises the benefit of quad-band and tri-band technology to attract buyers, frequency band information is also listed on the packaging. Generally, the frequency band listing will either appear as a list, like “GSM 850, GSM 900, GSM 1900," or as a series of relevant numbers separated by slashes, like 850/1800/1900. This information is usually available on the label inside the battery case on the phone.
The areas where a tri-band phone will operate best can vary depending on the frequency band range of the phone. Typically, tri-band phones operate on the 900/1800/1900 or 850/1800/1900 frequency bands, but some rare phones of this type use the 850/900/1900 frequency ranges. Tri-band technology is good for people who do limited travel, since the combined frequency range allows mobile access on most continents. Quad-band phones connect to 850/900/1800/1900, allowing for coverage in any country with a standard mobile phone signal. A person who does a great deal of traveling to different countries would benefit most from a quad-band GSM phone.
Quad-band and tri-band phones are more expensive than the more limited dual-band phones. Those designed for use in only one country can operate on fewer frequency bands. In the United States, many phones are dual-band, and will only work in the basic area in which they were bought. Most GSM phones in North America uses a combination of the frequency bands 800, 850 or 1900. Some dual-band phones are made for North America, including the United States, while some dual-band phones will only work in Europe, Asia, or Africa. Some dual-band phones can operate within limited international ranges, like 850/1800 phones, which work both in the United States and in India.