· 4B3T · 4B5B · 2B1Q · Hamming Code · 8b/10b encoding · 64b/66b encoding · 6b/8b encoding · 64b/66b encoding · MPlus used in DVD · Eight-to-Fourteen Modulation (EFM) used in Compact Disc · Conditioned Diphase · Coded mark inversion (CMI) · EF Carrier Suppressed Return-to-Zero Optical line code. · Alternate-Phase Return-to-Zero
Perhaps you mean 4B5B? That's a way to assign combinations of 5 bits to every combination of 4 bits, in such a way that you avoid transmitting long strings of only zeros or only ones. This avoids synchronization problems.
1101 => 11011 1010 => 10110 0011 => 10101 0001 => 01001 1000 => 10010 1001 => 10011 and together: 11011 10110 10101 01001 10010 10011