Commercial code (communications)

In telecommunication, a commercial code is a code once used to save on cablegram costs.Telegraph (and telex) charged per word sent, so companies which sent large volumes of telegrams developed codes to save money on tolls. Elaborate commercial codes which encoded complete phrases into single words were developed and published as codebooks of thousands of phrases and sentences with corresponding codewords. Commercial codes were not generally intended to keep telegrams private, as codes were widely published; they were usually cost-saving measures only.

Many general-purpose codes, such as the Acme Code and the ABC Code, were published and widely used between the 1870s and the 1950s, before the arrival of transatlantic telephone calls and next-day airmail rendered them obsolete. Numerous special-purpose codes were also developed and sold for fields as varied as aviation, car dealerships, insurance, and cinema, containing words and phrases commonly used in those professions.

These codes turned complete phrases into single words (commonly of five letters). These were not always genuine words; for example, codes contained "words" such as BYOXO ("Are you trying to weasel out of our deal?"), LIOUY ("Why do you not answer my question?"), BMULD ("You're a skunk!"), or AYYLU ("Not clearly coded, repeat more clearly.").

The first telegraphic codes were developed shortly after the advent of the telegraph, and spread rapidly: in 1854, one eighth of telegrams transmitted between New York and New Orleans were written in code. Cable tolls were charged by the word, and telegraph companies counted codewords like any other words, so a carefully constructed code could reduce message lengths enormously.

Early codes were typically compilations of phrases and corresponding codewords numbering in the tens of thousands. Codewords were chosen to be pronounceable words to minimize errors by telegraphers, and telegrams composed of non-pronounceable words cost significantly more. Regulations of the International Telegraph Union evolved over time; in 1879, it mandated coded telegrams only contain words from German, English, Spanish, French, Italian, Dutch, Portuguese, or Latin, but commercial codes already frequently used nonsense words. By 1903 regulations were changed to allow any pronounceable word no more than ten letters long.

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