"This standard defines the requirements for the transceiver of the pan-european digital mobile cellular and personal communication systems operating in the 900 MHz and 1800 MHz band (GSM 900 and DCS 1800). Requirements are defined for two categories of parameters: - those that are required to provide compatibility between the radio channels@ connected either to separate or common antennas@ that are used in the system. This category also includes parameters providing compatibility with existing systems in the same or adjacent frequency bands. - those that define the transmission quality of the system. This standard defines RF characteristics for the mobile station (MS) and base station system (BSS). The BSS will contain either base transceiver stations (BTS) or microcell base transceiver stations (micro-BTS). The precise measurement methods are specified in GSM 11.10 and 11.20. Unless otherwise stated@ the requirements defined in this standard apply to the full range of environmental conditions specified for the equipment (see Annex D). In this standard some relaxations are introduced for GSM 900 mobile stations which fulfill the following conditions: - pertain to power class 4 or 5 (see section 4.1.1); - have a total weight less than 200 g (excluding battery); - have a volume less than 500 cm3 (excluding battery). In this standard these mobile stations are referred to as ""small MS""."