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In those days, wireless signal codes worked rather as they did in the age of signal flags and sail. The words or phrases were in numbered groups, usually of five figures. The first numbers usually referred to the page of the codebook where the phrase was listed, the next number to the column and then the numbered code. It meant that signals could be pretty short, reducing the time the wireless was running, unless they were complex instructions or introducing orders that were very specific to the situation.
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