This document is for microwave detectors installed in buildings and provides for security grades 1 to 4 (see EN 50131-1), specific or non-specific wired or wire-free detectors, and uses environmental classes I to IV (see EN 50130-5). This document does not include requirements for detectors intended for use outdoors. The purpose of the detector is to emit microwave signals and analyse the signals that are returned to detect an intruder and to provide the necessary range of signals or messages to be used by the rest of the intrusion alarm system. The grade-dependent requirements of this document apply and it is essential that a detector fulfils all the requirements of the specified grade. Functions additional to the mandatory functions specified in this document can be included in the detector, providing they do not influence the correct operation of the mandatory functions. Requirements for system interconnections are not included in this document.