1. In combination: a plurality of distributed signal processing systems; each of said systems comprising a plurality of elements including a signal processor, a mass memory, and an input-output controller, and a first bus means for interconnecting in common said plurality of elements; said input-output controller of each one of said systems comprising a second bus means for interconnecting a plurality of said systems by coupling said second bus means to said first bus means of another of said systems and for providing coupling to a plurality of input-output data devices; and each of said elements comprising one or more bus transceivers and arbitration means coupled to one of said first and second bus means for determining the one of a plurality of elements connected to said one of the first and second bus means that obtains first use of said connected one of the first and second bus means when more than one of said elements attempt to use one of said first and second bus means simultaneously.