Extended GSM (E-GSM) is a term to denote the extended GSM band in the 900 MHz range. Extended GSM includes the standard GSM 900 band (GSM-P). The extension is an addition of 10 MHz at the lower side of the primary GSM 900 MHz band. This extension ranges from 880 - 890 MHz and from 925 - 935 MHz.
Including this extension, the extended GSM 900 band ranges from 880 - 915 MHz and from 925 - 960 MHz. Mobiles transmit in the lower band and base stations in the upper band.