I-G.703 (Co-Directional G.703) i-interface yahlula umjikelezo we-64Kbps kwiiyunithi ezi-4, isebenzisa "0101" imele "0", "1100" imele "1".Ngokutshintshisa i-polarity yenguqu yebhloko ekufutshane, imiqondiso yokubini iguqula imiqondiso yemigangatho emithathu.