Geiger–Müller tubes are the primary components of Geiger counters. They operate at an even higher voltage, selected such that each ion pair creates an avalanche, but by the emission of UV photons, multiple avalanches are created which spread along the anode wire, and the adjacent gas volume ionizes from as little as a single ion pair event. This is the "Geiger region" of operation. The current pulses produced by the ionising events are passed to processing electronics which can derive a visual display of count rate or radiation dose, and usually in the case of hand-held instruments, an audio device producing clicks.