SITOR recasts ITA2 into a 7 bit code called CCIR 476. Each 7-bit character in CCIR 476 has 4 marks (ones) and 3 spaces (zeros). Each valid character code has a Hamming distance of at least 2 from every other character. A one bit error will disrupt the balance of marks and spaces; a second bit error may (or may not) bring the count back to 4 marks and 3 spaces. Consequently, the CCIR 476 alphabet is guaranteed to detect all single bit errors within a character.