Description: nominal plane specified by a measurement standard to ensure comparability of results; Name: reference level
Description: horizontal plane for use as the datum for height measurement; Name: Reference plane
Description: norm/stipulation describing the explosion protection. The explosion protection type, the device category, the temperature class as well as the device / explosion group are taken from this norm. The type and number of the norm/stipulation with issue year and issue month must be given; Name: Reference norm of the explosion protection