Basedontheperiodicstructureofcodeworksoflinearblockcodes,anewideaoflength-varyingcodingdigitalcommunicationssystemisproposedtosavethechannel.Itisshown,byexample,thatupto1/3ofchannelcapacitycanbesavedbythenewsysteminsomespecialsituations.Inordertofindwhichblockcodeissuitabletouseinlength-varyingcodingsystem,theperioddistributionofthecodehastobecal-culated.Newrwsultsabouttheperioddistributionarepresentedwhilemanyopenproblemsremain.