ISO 7240-18:2017 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 7240-18:2017 can be used to assess this function. ISO 7240-18:2017 is applicable to input/output devices which include signal amplifiers and signal transfer in separate enclosures. Control and indicating equipment and ancillary control and indicating equipment (e.g. repeater panels and fire brigade panels) are not covered by ISO 7240-18:2017.