The 3-out-of-6 code is a coding method
used in radio transmission to achieve reliable parities. For this purpose, the level fluctuations on the receiving side must be kept as low as possible. In the 3-out-of-6 code, four-bit
long source symbols are converted into 6-bit long code words.This means that one third of the codeword, namely 4 out of 6, is inefficient. On the other hand, the generous conversion avoids uncertainties in the transmission.
The 3-out-of-6 code is used, among other things, in the wireless variant of the M-Bus, the Wireless M-Bus. In the wireless meter bus, the 3-out-of-6 coding maps useful bit sequences on specially selected sequences, whereby fixed bit sequences are used for the radio transmission.