30. The apparatus of claim 23 wherein said distributing means is provided with at least first and second outputs, each providing alternating odd and even information words in synchronism; and said odd and even error-correcting encoding means comprises error correcting word generating means coupled to said at least first and second outputs for generating at least one odd error-correcting word in response to odd information words provided at said outputs and generating at least one even error-correcting word in response to even information words provided at said outputs; time delay means for selectively delaying the information words provided at said outputs and the error-correcting word generated in response thereto to form a sub-block comprised of interleaved information and error-correcting words; and switch means for receiving each sub-block, said switch means having first and second sets of output terminals and operative when odd information words are provided at the outputs of said distributing means to couple an odd sub-block to said first set of output terminals and operative when even information words are provided at the outputs of said distributing means to couple an even sub-block to said second set of output terminals.
32. The apparatus of claim 30 wherein said error-correcting word generating means and time delay means comprise a P-parity generator for generating a P-parity word, the information words supplied to said P-parity generator and said P-parity word forming a P sub-block; first time delay means for selectively delaying the words of said P sub-block to interleave the information and P-parity words therein; a Q-parity generator for generating a Q-parity word in response to the interleaved words of said P sub-block, the interleaved words of said P sub-block and said Q-parity word forming a Q sub-block; and second time delay means for selectively delaying the words of said Q sub-block to interleave the information, P-parity and Q-parity words therein, each Q sub-block being supplied to said switch means.