The rapid adoption of the unlicensed 2.4 GHz industrial, scientific and medical (ISM) band for various radio telecommunication services has created a complex electromagnetic environment in which interference between services may occur. Examples of such services are the IEEE 802.11 wireless LAN system and digital cordless phones. Appendix I discusses the 2.4 GHz ISM band environment in more detail. Recommendation ITU-T K.79 characterizes the typical 2.4 GHz ISM band radiated EM environments for home, office and commercial locations as well as the train and the aeroplane. The environmental analysis uses both theoretical prediction and real measurements. The analysis includes multipath evaluation and the different modulation effects of the radio systems. Based on this analysis, proposals are made for interference levels and specific electronic equipment susceptibility levels.