A complete scaling unit for counting regular or random pulses is described. The unit employs cold-cathode scaling tubes and trigger tubes in the main counting circuits. Various methods of driving cold-cathode scaling tubes are fully described. A novel method of driving the CV2271 scaling tubes is used in which the amplitudes and durations of the pulses to all stages in a cascade of these tubes are controlled directly by a common pulse generator, and cold-cathode trigger tubes are used as gating elements between the stages. A new type of pulse amplitude discriminator of high sensitivity is used at the input of the scaling unit. A simple system of marginal testing of the complete equipment is incorporated in order to obtain early indication of deterioration of tube characteristics.