Dual rail time and control unit for a T-S-T-digital switching system

Claim 1

In a time-space-time switching system including first and a second buses, each bus transmitting a plurality of PCM voice samples to a switching network, said buses connected between said network and subscriber interface equipment, said switching network comprising: first and second space switching means; first and second originating time switching means, each of said originating time switching means being operated to switch said PCM voice samples from said subscriber interface equipment, said first and second originating time switching means being connected respectively between said first and second space switching means and said subscriber interface equipment via said first and second buses; each of said originating time switching means including: first and second memory means connected to each of said first and second buses, said first and said second memory means being interconnected so that said first and said second memory means are written into simultaneously in sequential time slots with said PCM samples transmitted via said buses; said first and said second memory means further being operated so that said PCM samples transmitted on said first bus may be switched to said second space switching means for subsequent retransmission and alternatively said PCM samples transmitted on said second bus may be switched to said first space switching means for subsequent retransmission; first and second terminating time switching means being connected respectively between said first and said second space switching means and said subscriber interface equipment, said first and second terminating time switching means respectively operated to switch said PCM voice samples from said first and second space switching means to said subscriber interface equipment for transmission to a telephone subscriber; each of said terminating time switching means including: first and second memory means connected between each of said first and second space switching means and said subscriber interface equipment, said first and said second memory means being interconnected so that said first and said second memory means are written into simultaneously in corresponding time slots for storing said PCM samples transmitted from said space switching means; a plurality of buses connected between each of said memory means of said terminating time switching means and said subscriber interface equipment for transmitting said PCM samples to said subscriber interface equipment; gating means connected respectively between said first and second space switching means and interconnected to each of said memory means of said first and second terminating time switching means, each of said gating means being operated in response to said memory means of said terminating time switching means to transmit said PCM samples from said first and second space switching means to said first and second memory means for each of said plurality of PCM samples; and said first and said second memory means further being capable of being operated to switch said PCM samples from said first space switching means through said second terminating time switching means to said telephone subscriber and alternatively being capable of being operated to switch said PCM samples from said second space switching means through said first terminating time switching means to said telephone subscriber.