The detector is an industrial standard model of a Geiger-Müller tube, with a thin mica output window.
It is factory-calibrated using a pulse generator, and is usually ±15% of the full scale relative to Cesium-137.
It carries out detections in milliroentgens/hour and in events/minute (cpm) in three different measurement intervals. The unit is protected by an antisaturation circuit up to a value equivalent to 100 times the maximum reading in the greatest interval. The radiation detected is indicated by the hand moving on the graduated scale, a blinking LED and an audible beeper.