Extended GSM (E-GSM) refers to an extension of the standard GSM 900 MHz band. It includes the original GSM 900 band and adds 10 MHz to the lower side of the spectrum, spanning from 880 to 890 MHz and from 925 to 935 MHz. In total, the extended GSM 900 band covers frequencies from 880 to 915 MHz and from 925 to 960 MHz. Mobile devices operate in the lower band, while base stations use the upper band.