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

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 connected respectively to said first and second space switching means and connected to said subscriber interface equipment via said first and second buses, each of said originating time switching means operated to switch said PCM voice samples to said first and second space switching means respectively;
• first and second terminating time switching means, said first and second terminating time switching means connected respectively between said first and said second space switching means and said subscriber interface equipment, said first and second terminating time switching means operating to switch said PCM voice samples from said first and second space switching means to said subscriber interface equipment;
• each of said terminating time switching means including:
• memory means connected between 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;
• gating means connected respectively between said first and second space switching means and each of said memory means of said first and second terminating time switching means, each of said gating means operating respectively 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 operable so that said PCM samples from said first space switching means are switched through said second terminating time switching means or alternatively to switch said PCM samples from said second space switching means through said first terminating time switching means.