Similarly, the number 2 in an odd slot corresponds to 1 in an even slot.
Where an odd slot shows a 1, an even one shows a 5, so entering a 5 in an even slot is equivalent to entering a 1 in an odd slot. If we number the slots from the right, starting with 1, the even-numbered input slots have a strange digit distribution. It looks like an ordinary chain adder, but it does not have a tens carry and all chains add to the same number in the small window at the far right. Luhn invented a mechanical calculator for this checksum (, Figure 4). The calculation of a checksum has to be fast and not error-prone, so it is useful to mechanize this calculation. Other telegram condensers do show checksums in the final message, and sometimes even checksums that contain a check digit to check themselves. When decoding an erroneous message an inconsistency occurs between the possible checksums indicated by the encoding scheme and the checksums of the decoded message. The checksums themselves are not part of the final message, so do not increase the transmission costs directly, but they force the encoding to be not the most efficient one. This final encoding is controlled by the checksums. First common words and phrases are expressed in small numbers using a dictionary, then an intermediate checksum is calculated per five 2-digit numbers, and finally the 2-digit numbers are encoded in 2-character codes.
#Calculate the 9 bit binary checksum calculator code#
The aim of the Mosse Code is to lower the costs of telegrams by reducing their size. This is, for example, the case in the Rudolf Mosse Code Condenser for telegrams. Checksums are not always explicitly visible in the actual number.
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