16 CLAIMS

• 1. A distributed control switching network having a plurality of stages of switching elements for selectively interconnecting a plurality of data terminals over transmission paths thru said network established in response to digital command signals, and for transmitting frames of digitally encoded data in a plurality of channels from said data terminals over said established transmission paths, comprising:
• means for multiplexing said frames of data from said plurality of data terminals onto said transmission paths established by said digital command signals and in the channels designated by said command signals;
• common transmission link means having said digital command signals and said digitally encoded data from said plurality of data terminals coupled thereto, said transmission link means being coupled to the first stage of said switching network;
• means at each stage of said switching network responsive to said digital command signals for establishing said transmission paths stage-by-stage through said network such that said data is transmitted over said established transmission paths in the channels designated by said digital command signals; and
• means associated with each of said switching elements at each stage of said network for phase-asynchronously coupling said data from switching elements in any stage of said network to switching elements in any other stage of said network over said established transmission paths and including means for phase-synchronization of said data.
• 2. A distributed control switching network in accordance with claim 1 wherein said digital switching network comprises a multistage group switch, each stage thereof being comprised of a plurality of multiport switching elements.
• 3. A distributed control digital switching network in accordance with claim 2 wherein each of the switching elements of said stages of said network includes means for space and time switching said digitally encoded data from any channel at the input of the port of said multiport switching element receiving said channel to any channel at the output of any port of said multiport element in response to said digital command signals received by said port for said channel and in said channel.
• 4. A distributed control digital switching network in accordance with claim 3 wherein said digital command signals are in-channel switching path selection control signals.
• 5. A distributed control digital switching network in accordance with claim 4 further comprising:
• means for providing a plurality of switching path selection control signals for each connection path to be established thru said network;
• means at the switching elements of each stage of said network responsive to one of said switching path selection control signals for setting up a connection thru said stage; and
• means at the highest numbered stage required to complete said connection for folding back said path thru the network by reflecting at said highest numbered stage.
• 6. A distributed control switching system in accordance with claim 5 wherein connections from the reflecting stage to the terminal addressed by said switching path selection control signals are coupled thru ports of switching elements selected by the terminal addressed by said switching path selection control signals.
• 7. A distributed control switching network in accordance with claim 3 wherein said switching network includes a plurality of planes of stages of switching elements, at least some of said planes being coupled to each of the terminals via access switching means coupled to the common transmission links.
• 8. A distributed control switching network in accordance with claim 7 wherein said digitally encoded data from said terminals is comprised of digitally encoded PCM speech samples which are transmitted in the same channel and on the same transmission path as the digital command signals which designated said channel and said transmission path.
• 9. A distributed control switching system in accordance with claim 1 wherein said switching elements are operable as either single-sided or multi-sided switching elements within said switching network in accordance with the position of said switching elements within said network with respect to said established transmission paths.
• 10. A distributed control digital switching network in accordance with claim 3 further comprising:
• means at each switching element responsive to one of said digital command signals for setting up a connection thru said switching element at its stage of said switching network such that a connection thru a plurality of stages of switching elements is set up by a plurality of digital command signals, stage-by-stage, one of said digital command signals being used to set up said path thru each stage.
• 11. An expandable switching network comprising:
• a plurality of stages of multiport switching elements, each of said elements including:
• means for providing and maintaining time and space switching between any inlet port thereof and any outlet port thereof for frames of digitally encoded data in a plurality of channels;
• means for selectively reflecting phase asynchronous digitally encoded data entering any inlet port of said switching element back to any inlet port of said switching element;
• means for phase synchronizing said data frames on a time division multiplexed common transmission bus; and
• means for adapting each of said switching elements to either couple said phase synchronized digitally encoded data thru said switching element to another switching element in a higher numbered stage of said network or fold said digitally encoded data into the network by reflecting from a higher numbered stage to a lower numbered stage of said network.
• 12. An expandable switching network in accordance with claim 11 further comprising:
• means for establishing paths through said switching network in response to path selection control signals such that one in-channel address word in said path selection control signal per stage is required to establish a path between any port of a switching element in any stage and any port of said switching element in the same stage in said switching network, said path being established to any free port in said switching element; and
• means for establishing a reflecting path through said network with a single constant data address at the highest numbered stage of said network required to complete a path for said digitally encoded data thru said network.
• 13. An expandable switching network in accordance with claim 12 wherein said digitally encoded data is comprised of digitally encoded PCM speech samples and wherein each of said switching elements includes means for providing phase and word resynchronization of said data.
• 14. An expandable switching network in accordance with claim 13 wherein each of said switching elements includes:
• means for coupling data from any input channel of any port to a bit synchronous time division multiplex bus;
• means for providing space switching of data from said bus to any port; and
• means for providing time switching of data from said time division multiplex bus to any output channel of any port.
• 15. An expandable switching network comprising:
• a plurality of stages of multiport switching elements operable within said network as single sided or multisided, each port of each switching element including means for adapting said port for operation as an inlet or as an outlet and each of said switching elements including means to selectively reflect phase asynchronously received frames of digitally encoded traffic in a plurality of channels entering any inlet of any port of said switching element back to any inlet of any port of said switching element and to phase synchronously interconnect any outlet port of said switching element to any outlet port of said switching element; and
• means for selecting the inlets and outlets of each port of each of said switching elements for single sided or multisided operation within said network such that said inlet and outlet ports either selectively couple traffic through said switching element to a switching element in a higher numbered stage of said network or fold said traffic into the network by reflecting from a higher numbered stage to a lower numbered stage of said network.
• 16. A method of interconnecting a plurality of data terminals thru a multistage distributed control digital switching network comprised of a plurality of switching elements at each stage, and having common transmission paths for data and control channels thru said network comprising the steps of:
• multiplexing data from said plurality of terminals and control signals, including at least switching path selection control signals, onto common transmission links coupled to the first stage of said network;
• setting up transmission paths thru said network in response to said control signals for switching phase asynchronously received data and said control signals from said terminals thru said network on said set-up transmission paths; and
• intercoupling said switching elements at each stage of said network for phase asynchronously coupling said data thru said network via said transmission paths set up through said network such that said data is phase resynchronized by each switching element and such that any of said terminals may be selectively interconnected by said set up transmission paths through said network to any other of said terminals.