What is triband in mobile phones?

Tri band phones (also known as tri-band or triband) are mobile phones that support three frequency bands. Having more than one frequency in one device is useful to enable roaming between different countries that peg the allowed transmission frequency at different values or to allow a better coverage in the same country.
Various countries use different frequency bands for their mobile networks, and a triband phone can be used on three of these bands, generally speaking, chosen to favour two of the home country's bands, and one for roaming in other countries.

In summary GSM frequency bands used around the world are:

* 850 MHz (In America)
* 900 MHz (In Europe and many parts of Asia)
* 1800 MHz (In Europe and Asia)
* 1900 MHz (In America)

2G Triband phones are mobile phones that support the GSM 900/1800/1900 MHz bands (commonly sold in Europe, Asia, and Africa), or alternatively the 850/1800/1900 bands (commonly sold in the Americas). The Motorola V300 formerly carried by Rogers Wireless used a rare combination of 850/900/1900.

A 2G Quad band (850/900/1800/1900) offers more coverage and is now quite common.

Further information: UMTS frequency bands

UMTS / HSDPA devices operate in UMTS frequency bands 850/1900/2100 or 850/1700/2100 MHz:

* 2100 (downlink) / 1900 (uplink) for Europe and Asia (usually referred simply as W-CDMA 2100)
* 1900 / 850 (independently, for both the uplink and downlink) for America (e.g. Cingular Wireless)
* 2100 (downlink) / 1700 (uplink) for America (e.g. T-Mobile)

UMTS / HSDPA / HSUPA is a further evolution.

Note that being UMTS / HSDPA / HSUPA tri band doesn't mean that phone is a GSM / GPRS / EDGE tri band. An HSUPA tri band might not be a GSM at all. However nearly all HSDPA or HSUPA tri band are EDGE quad band too.

A 3G Quad band offers more coverage.

Devices

Some UMTS / HSDPA 850/1900/2100 tri band are already available:

* ASUS - P750
* BandRich - BandLuxe C100
* HTC – HTC TyTN, HTC P3600, HTC Advantage X7500, HTC Shift (Ultra-Mobile PC), HTC S420, HTC S630, HTC P4550, HTC P6500, HTC Touch Cruise
* Huawei – E800 Data Card (ExpressCard)
* i-mate – JASJAM, Ultimate series 5150 6150 7150 8150 9150 (all five available alternatively in 850/1700/2100 bands)
* Palm - Treo 750 (UMTS only)
* Sony Ericsson – PC300, Z750, K850i, MD300
* UBiQUiO - 503G

Some UMTS / HSDPA / HSUPA 850/1900/2100 tri band are already available:

* HTC - HTC Omni
* Huawei – E270 Wireless modem (USB)
* Novatel Wireless – Merlin X950D ExpressCard
* Option – GlobeTrotter Express HSUPA, GlobeTrotter GT MAX HSUPA, GlobeSurfer iCON HSUPA, GTM380
* Sierra Wireless – AirCard 880 and the AirCard 881 (PC Card), AirCard 880E and the AirCard 881E (ExpressCard) and MC8780 and the MC8781 (PCI Express