1. An arbiter for arbitrating between a plurality of input signals comprising: an input terminal for receiving the plurality of input signals; an output terminal for outputting a priority output signal specifying priority for one of the plurality of input signals; first correlating means for receiving the plurality of input signals, for generating groups of input signals and for comparing the groups of input signals to output a selected group of input signals having at least one input signal having priority over the input signals of all other groups; second correlating means for receiving the input signals of the selected group and the plurality of input signals and for comparing the input signals of the selected group and the plurality of input signals to select a selected input signal from the selected group having a priority over the other input signals of the selected group and for thereupon supplying the priority output signal to the output terminal, thereby arbitrating between the plurality of input signals under the control of the input signals themselves.