What if you are travelling to a foreign country and you need to know if your phone will work there? The answer is simple. There are two things to check:
1. GSM frequencies for making telephone calls (some phones use CDMA,these are not dealt with here)
2. Data service frequencies for accessing the Internet.
There are two GSM frequency groups:
1. 900 and 1800 Mega Hertz (MHz)
2. 850 and 1900MHz.
Most of the world is in the first category except USA. See the map.
The next question is: Now that I have found that USA uses 850 and 1900MHz for making telephone calls, can my phone use these frequencies?
As an example, take the LG Optimus L3 E400. What are the GSM frequencies of this phone? You can get these details from the http://www.gsmarena.com/ website. If you search for LG E400, you will get the following page.
For this phone, the key frequencies are:2G Network GSM 850 / 900 / 1800 / 1900
3G Network HSDPA 900 / 2100
This data says that your phone can use both the 850/1900 and 900/1800 bands for GSM and 2G Internet (EDGE)
Therefore, LG E400 will work in the USA for phone calls and 2G Internet.