25. The apparatus of claim 23 wherein said odd and even error-correcting encoding means is formed of separate encoding means, each comprising error-correcting word generating means for generating at least one error-correcting word in response to the information words supplied thereto, and time delay means for selectively delaying the information and at least one error-correcting words to form a sub-block comprised of interleaved information and error-correcting words.
27. The apparatus of claim 25 wherein said error-correcting word generating means and time delay means comprise a P-parity generator for generating a P-parity word, said 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.