ISO 7240-1:2005 provides a set of general guidelines and definitions to be used in describing the fire detection and alarm system equipment, tests and requirements in the other parts of ISO 7240. The components that a fire detection and alarm system can have are shown in Figure 1. Item C of Figure 1 can be replaced by a sound system for emergency purposes, the components of which are shown in Figure 2. Fire detectors can be self-contained: these are devices containing within one housing all the components, except possibly the energy source, necessary for detection of fire and giving an audible alarm. Inter-connected smoke alarms complying with ISO 12239 and not connected to control and indicating equipment do not form a fire detection and alarm system as defined in ISO 7240-1:2005.