Frame format for PCM speech data in a telephone transmission system and digital telephone apparatus for use with this frame format

Digital telephone apparatus for transmitting and receiving PCM speech data as well as signalling information via a telephone transmission line, said apparatus comprising, in combination:

• (a) a serial frame synchronizer, adapted to receive serial digital information that was transmitted over said transmission line, said serial frame synchronizer decoding a synchronizing code in said serial digital information and thereby identifying the timing of successive, 125 microsecond frames of data;
• (b) a sync/signalling generator connected to said serial frame synchronizer and adapted to transmit serial digital information over said transmission line, said sync/signalling generator being responsive to a first enable signal received from said serial frame synchronizer for shifting out to said transmission line a first outgoing 8 bit data word comprising a synchronization code and a signalling code;
• (c) a first codec/PCM filter connected to said serial frame synchronizer and adapted to transmit serial digital information over said transmission line, said first codec/PCM filter being responsive to a second enable signal from said serial frame synchronizer for shifting out to said transmission line a second outgoing 8 bit data word comprising a PCM speech sample, said second outgoing 8 bit word immediately following said first outgoing 8 bit data word;
• and,
• (d) means for generating a third outgoing 8 bit data word connected to said serial frame synchronizer and adapted to transmit serial digital information over said transmission line, said means for generating said third outgoing 8 bit data word being responsive to a third enable signal from said serial frame synchronizer for shifting out to said transmission line said third outgoing 8 bit data word, said third outgoing 8 bit data word immediately following said second outgoing 8 bit data word.