What are SIM cards and GSM?
In the last few years, SIM cards that are made especially for international calling have lowered the cost of calling home from abroad to manageable, even quite cheap levels. All handsets that use SIM Cards are GSM handsets. GSM stands for Global System for Mobile Communications. SIM cards let your phone know who your service provider is and what your plan and rates will be. U.S. carriers AT&T Wireless and T-Mobile and Canadian carrier Rogers all use this GSM technology. Phones that use GSM all have SIM cards installed, but will they work overseas when you insert an International SIM card? Purchasing an SIM card prior to travel provides some nice advantages. For example a traveler from the U.S. flying over to the U.K. can purchase a SIM card online, have it shipped to their home and be ready to call from Europe as soon as they land at Heathrow. International SIM cards and Global SIM cards can be used to call locally or back home without paying hefty roaming charges from your regular car
