22 CLAIMS

• 1. A distributed control digital communication system for selectively interconnecting a plurality of groups of terminals thru a digital switching network having an access switching stage and one or more other switching stages, comprising:
• a first group of data processing means for providing a first set of pooled processing functions for said groups of terminals, each of said processing means being associated with one of said groups of terminals;
• a second group of data processing means for providing a second set of pooled processing functions for one or more of said groups of terminals such that said second processing functions are provided independently of the processing functions provided by said first group of processing means; and
• digital switching network means coupled to said first and second groups of processing means by one or more multiplexed transmission paths over which data and at least path selection control signals are transmitted in frames containing a plurality of channels of said data, such that said path selection control signals establish communication over said multiplexed transmission paths thru said digital switching network means between said first and second groups of data processing means with said path selection control signals preceding said data on said multiplexed transmission paths in the same channels and selectively interconnect said terminals over transmission paths thru said switching network in channels designated by said path selection control signals.
• 2. A distributed control system in accordance with claim 1 wherein said multiplexed transmission paths are bidirectional transmission links.
• 3. A distributed control system in accordance with claim 1 wherein said data and control signals are transmitted over said transmission paths bit-asynchronously.
• 4. A distributed control digital communication system in accordance with claim 1 further comprising a plurality of terminal unit means, each of said terminal unit means having coupled thereto a plurality of said groups of terminals and including means for multiplexing data from said terminals onto said transmission links together with said path selection control signals.
• 5. A distributed control digital communication system in accordance with claim 1 wherein each data processing means of the first group of data processing means is coupled to at least two access switching means having said multiplexed transmission paths coupled to inputs thereof and having outputs coupled therefrom to said multiplexed transmission paths upon which said data between said terminals and said path selection control signals are multiplexed to said digital switching network.
• 6. A distributed control digital communication system in accordance with claim 1 wherein each data processing means of the second group of data processing means is coupled to one or more access switching means having said multiplexed transmission paths coupled to inputs thereof and has outputs coupled therefrom to said multiplexed transmission paths upon which said data is coupled between each data processing means of said second group of data processing means and said switching network.
• 7. A distributed control digital communication system in accordance with claim 1 wherein said data comprises frames of digitally encoded PCM speech samples in a plurality of channels from telephone lines circuits.
• 8. A distributed control digital communication system in accordance with claim 1 wherein said data comprises frames of digitally encoded PCM speech samples in a plurality of channels from telephone trunk circuits.
• 9. A distributed control system in accordance with claim 5 wherein each of said data processing means of said second group provides a set of pooled processing functions accessible over said multiplexed transmission paths by any of the data processing means of the first group.
• 10. A distributed control digital communication system in accordance with claim 1 wherein said digital switching network comprises an expandable group switch comprised of a plurality of switching elements, each of said elements having two or more inlets and two or more outlets and being adapted to selectively reflect traffic entering any inlet of said switching element back to any other inlet of said switching element and for connecting the outlets of said switching element to the inlets of other switching stages.
• 11. A distributed control digital communication system in accordance with claim 1 wherein the data processing means of said first and second groups of data processing means are microcomputers.
• 12. A distributed control digital communication system in accordance with claim 1 wherein said switching stages of said switching network are comprised of switching elements operable as either single sided switching elements or multisided switching elements within said switching network.
• 13. A distributed control digital communication system in accordance with claim 5 wherein each data processing means of said first group of data processing means is adapted to provide as processing functions at least path set up and terminal device supervision for its respective group of terminals and wherein each of said second group of data processing means is adapted to provide as a processing function at least call control for its respective group of terminals.
• 14. A distributed control digital communication system in accordance with claim 13 wherein each processing means of said second group of processing means is further adapted to provide call translation as a processing function for its respective group of terminals.
• 15. A distributed control digital communication system comprising a plurality of terminal units for interfacing a plurality of PCM communication terminals carrying digitized speech in frames containing a plurality of channels of said digitized speech to a common communications path upon which said frames and in-channel path selection control signals are multiplexed, and comprising:
• means for deriving at least digital path selection control signals for each PCM terminal interfaced thereto;
• a digital switching network coupled to said communications path for bit asynchronously interconnecting said PCM terminals through paths established thru said switching network in response to said in-channel path selection control signals, and;
• means at each of said terminal units for selectively multiplexing said digitized speech and said in-channel path selection control signals on said common communications path such that said digital path selection control signals precede said digitized speech in channels designated by said path selection control signals on said common communications path.
• 16. A distributed control digital communication system in accordance with claim 15 wherein said switching network is comprised of a multistage group switch.
• 17. A distributed control digital communication system in accordance with claim 15 wherein each of said means for deriving said path selection control signals for a group of said PCM terminals comprises one processor of a group of processors.
• 18. A distributed control digital communication system in accordance with claim 15 wherein said PCM terminals each are associated with a telephone subscriber line.
• 19. A distributed control communication system in accordance with claim 15 wherein said PCM terminals each are associated with a telephone trunk line.
• 20. A distributed control digital communication system in accordance with claim 17 further comprising:
• a second group of processors, each of said processors of said second group of processors providing other processing functions for a plurality of said groups of PCM terminals; and
• means for coupling interprocessor control signals from one processor of a group of processors to any other processor through said paths established thru said switching network by said path selection control signals to provide communication therebetween.
• 21. A distributed control digital communication system in accordance with claim 19 wherein at least one of the processing functions provided by each of the processors of said second group of processors includes call translation.
• 22. A method of communicating between a plurality of terminals having data in frames containing a plurality of channels of said data coupled thereto, wherein a plurality of groups of said terminals are selectively interconnected thru a digital switching network in response to in-channel path selection commands, comprising the steps of:
• deriving a first set of processing functions including said in-channel path selection commands for said groups of terminals, said processing functions being derived by a first plurality of processors in a first group of said processors;
• deriving a second set of processing functions by a second plurality of processors in a second group of processors for one or more of said groups of terminals such that said second set of processing functions are derived independently of the first set of processing functions; and
• interconnecting said first and second pluralities of processors thru a digital switching network coupled to the first and second pluralities of processors by one or more multiplexed bidirectional transmission links over which data and at least path selection control signals are bit-asynchronously transmitted to provide interconnection between said first and second pluralities of processors in channels designated by said commands and selective interconnection of said data in said channels between said terminals over common transmission paths thru said switching network established by said path selection control signals.