This part of ISO 7240 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 this part of ISO 7240 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 this part of ISO 7240 shall apply. Control and indicating equipment and ancillary control and indicating equipment (e.g. repeater panels and fire brigade panels) are not covered by this part of ISO 7240.