What is the meaning of this? GSM 850 900 1800 1900

[Reland]

How do I know which one I'm using or which one my next phone needs to use? If I buy a tri-band phone from the UK will it work well with T-Mobile in NY? If I'm not mistaken my current phone (Samsung x105) uses only GSM 900 and 1900 and I get a strong signal almost everywhere on Long Island, so any tri-band or quad-band GSM phone should be okay, right?

Have SIM cards changed at all in the last two years? I've only ever had one and I haven't tried it in a current hi-tech phone.

Specifically I'm interested in the Sony Ericsson W800 or W800i, but what is the "i" for? I've read the W800c is for mainland China but what's the difference between "i" or no "i"?

I know I'll get a good answer from someone on this board, so thanks in advance.

[Sven Johannsen]

The numbers are, of course the broadcast frequency (or band of them) at which the phone works. They are liscenced by the carriers from the FCC and other regulatory agencies around the country. Sometimes one carrier has all of one band locked up in an area and another carrier needs to use another band. The four you mentioned are the four most used bands throughout the world, so if you have them all in your phone you should be good to go about anywhere you go that has GSM coverage. A good place to see who uses what is at

http://www.gsmworld.com/roaming/gsminfo/index.shtml

Yea about any tri or quad band should work in NY since they all seem to cover 1900. If it's tri, it will matter what three are used if you travel. A quad is better and are typically called world phones for that reason.

I'm pretty sure your current SIM should work in today's phones. I've got SIMs that old or older in current i-Mates. You could see if someone you know has a more modern T-Mobile or unlocked phone and try it.