Mobile Phone Frequencies

Mobile phone tri-band generally refers to 900MHZ, 1800MHZ, 1900Mhz.

1900MHz is the U.S. GSM band.

900MHZ band is the frequencies of G mobile network, 1800MHz is the D-band network.
Therefore, 3-band phone will switch between 900 and 1800 frequency bands.
Which band specific choose will depend on network parameters at that time.
British bands are now using WCDMA and GSM, China's GSM is imported from Europe. Phone frequency divided into dual, tri-band, quad-band. Dual-band is not only use in China, you can also use dual-band GSM phone in the UK. Tri-band cell phone can be used in most of the parts of the world, the United Kingdom are also allowed. While the 4-band frequency added another frequency on the basis of the tri-band frequency, the signal will be better in some countries.

1900M band only in the Americas, such as the United States (the United States is 900M/1800M/1900 co-exist), New Zealand 900M/1900M, there is a network of 1900M band in Paraguay, so if we go abroad to these countries must take a tri-band mobile phone, like Triband Camera Cell Phone, Unlocked 2.4" M188 Tri-Band GSM PDA Cell Phone, GPS IPTV Tri-band PDA Mobile Phone and so on.
Currently Ecuador Conecel company uses 850M band need to use a quad-band phone to connect with others, such as the HTC Quadband PDA Cell Phone with Windows Mobile Phone 6.0, HTC Quad Band GPS/MSN/Emial/WiFi PDA.