The 5B6B coding method is used in 100Base-VG and represents 5-bit words via coding tables in the form of 6-bit symbols. Of the 32 6-bit symbols, 20 are DC neutral, i.e. they have an identical number of ones and zeros and are therefore also referred to as "balanced".
The remaining twelve 6-bit symbols, called "unbalanced", are defined in two groups of 12 symbols each with two ones and with four ones. This measure is necessary in order to be able to transmit unbalanced symbols without DC current. For this purpose, when successive unbalanced symbols are transmitted, one symbol from each group (with two ones) is alternately transmitted followed by one symbol from the other group (with four ones). This process results in a balanced bit sequence of ones and zeros, and thus a DC-free transmission. Compared to 4B5B coding, this procedure increases the step rate.