UHF RFID systems are required to work at different frequencies depending on the country of operation. For example, in the USA they can operate between 908 MHz and 928 MHz, while in Europe they operate from 865 MHz to 868 MHz. Not only does the frequency vary with country of operation but so does the RF power that can be legally transmitted. It is 4 Watts Effective Isotropic Radiated Power (EIRP) in the USA but only 2 Watts Effective Radiated Power (ERP) in Europe.