This European Telecommunication Standard (ETS) gives an overview of the tasks undertaken by a GSM mobile station (MS) when in idle mode, that is, switched on but not having a dedicated channel allocated, e.g. not making or receiving a call. It also describes the corresponding network functions. NOTE: The term GSM MS is used for any type of MS supporting one, or combinations, of the frequency bands specified in GSM 05.05 (e.g. GSM 900 and DCS 1800). This ETS outlines how the requirements of the GSM 02 series Technical Specifications (especially GSM 02.11) on idle mode operation shall be implemented. Further details are given in GSM 04.08 and GSM 05.08. Clause 2 of this ETS gives a general description of the idle mode process. Clause 3 outlines the main requirements and technical solutions of those requirements. Clause 4 describes the processes used in idle mode. There is inevitably some overlap between these clauses.