GSM-Cell-Phone Demystified, What is GSM?

GSM-Cell-Phone is the abbreviation for Global System For Mobile Communications. It is an improved version of TDMA and a hybrid of Analog and TDMA. This is the standard developed to work throughout Europe and most of Asia. A GSM-Cell-Phone will always have a Sim Card. T-Mobile, Cingular use the GSM type of digital system in the US.

The 4 different GSM Frequencies

850, 900, 1800, 1900. Most of Europe and Asia use 900/1800 GSM Cellular frequencies. Most of the US and Canada GSM systems are 1800 and also starting to be 850 (the old analog Cell Frequency). The 850 Frequency allows a little larger area to be covered per tower which works well in more rural areas.

Unlocked VS Locked GSM Phones

A locked GSM phone will only work on the network that sold the phone. This would be like Cingular, AT&T, or T-Mobile.

The lock is actually a software switch that the vendor progams into the phone after they get the phone from manufacturer and before they sell it.

T-Mobile will currently unlock the phone you purchase with a plan from them after 90 days. At&t will normally not unlock the phone from them under any circumstances.

Cingular will sell some phones unlocked and others locked.

My question is if I purchase this phone who owns it, So why can't I unlock my GSM-Cell-Phone?

Help Unlocking Your Phone

There are some websites that claim to be able unlock a locked phone. I do not have experience with this but this website seems to have a lot of information involving GSM cell phones ---

Dual Band, Tri-Band, Quad-Band GSM

Some of the original GSM phones will only work on one band. Dual-Band,Tri-band, Quad-Band phones come in several varieties. Be careful to check which bands the phone you are looking at works on. To use a phone in Europe and Asia it is best to have access to both the 900 and 1800 frequencies. For use in the US I would definitely want a phone that works on both the 850 and 1900 Frequency.

T-Mobile GSM-Cell-Phone Prepaid Strategies Page.


In the United States the Cell standard wars are raging. Verizon and Alltel/Cell One are using the CDMA standard. T-Mobile and Cingular are using the GSM standard. Most of Europe, Asia and the rest of the world are using GSM also. There is an advantage to GSM because any equipment developed can be sold anywhere in the world. That is why usually the really nice high end phones become available for GSM first. The CDMA standard has enough volume that it is really competitive too. It will be interesting to watch the Cell company mergers.