The Check Value was quoted, as were the contents it checked against, but the value inside was the check of the "unquoted" values. That means that Body had to be extracted and unquoted before the Check Value could be calculated on the receiving end. Four types of Check Values were allowed, the original XMODEM checksum, a slightly modified version of the cyclic redundancy check (CRC) used in XMODEM-CRC, or the CCITT CRC-16 or CRC-32. When using the CCITT CRC, the Trailer also included an optional character at the end as a "network break" (send now), although it is not clear why this was "not" supported with other Trailer types.