Abstract: A radiation detector such as a proportional counter produces pulses of wh the peak voltage is representative of radiation energy and the pulse rate is representative of radiation intensity. These pulses are sorted out according to peak voltage and the pulses in each peak voltage range are individually counted. Each channel has an AND-gate with one input receiving a signal from a flipflop which is set when a differential amplifier of that channel detects an input pulse voltage exceeding a predetermined bias and the AND-gate also has another input connected to the negative output of the flipflop of the next higher channel. The bias voltage of differential amplifiers sets the lower threshold of each channel, of which the upper threshold is the lower threshold of the next higher channel. When a transfer pulse is applied to the AND-gates, only the counter of the channel for the range within which the peak voltage of the detected pulse lies receives a pulse.