ISO 7240-18:2009 specifies requirements, test methods and performance criteria for input/output devices connected to a transmission path of a fire detection and alarm system used to receive and/or transmit signals to or from the transmission path, necessary for the operation of the fire detection and fire alarm system and/or fire protection system. An input/output device can be a physically separate device or its function can be integrated into another device, in which case ISO 7240-18:2009 can be used to assess this function. An input/output device can include signal amplifiers and signal transfer in separate enclosures, in which case the requirements of ISO 7240-18:2009 shall apply. Control and indicating equipment and ancillary control and indicating equipment (e.g. repeater panels and fire brigade panels) are not covered by ISO 7240-18:2009.