How does the 4B3T encoding method work?

Question

Algorithms

Hey!
Tell me , please, how does the 4B3T encoding method encode if the number of input bits is less than 4?
And what do columns 1, 2, 3, 4 mean in the table?

Answer 1

We start with some sum, for example, 2.
bits 0000, sum 2 - according to the table 0−0, subtract 1 from the sum, it turns out 1.
Bits 0000 come again, sum 1 - already +0+ according to the table, add 2 to the sum , it turns out 3.
This is how we balance the average current through the communication channel at zero.