Apparatus and method for voting out a malfunctioning channel in a system of channels carrying electric pulses. The pulses may be produced by particles passing through a sensing zone. The pulses are conducted through comparison and exclusion stages. A device for producing mean size values of the pulses is placed ahead of the comparison stage so that comparison and exclusion are performed on the basis of the mean size values of the pulses. In another embodiment, channels for counting the pulses are provided with count threshold circuits of the counting channels being positioned ahead of the devices for producing the mean size values of the pulses.