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Author Topic: Deciphering coded radiograms  (Read 7319 times)

Gary LaPook

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Deciphering coded radiograms
« on: January 21, 2012, 07:55:19 PM »

If you have researched the telegrams available at the Purdue website, you have come upon radiograms that appeared to be in some secret code, consisting of groups of five numerals, probably left you scratching your head. Well they are in code, but not a secret code. The code is the open code named the International Radio Weather Code For Use On United States Selected Ships. published in 1930. This code provides the method to compress weather reports into just a few short groups for transmission by radiogram. Why do this? Because telegrams and radiograms were expensive, you were charged by the word or by the five digit group. Because of the high cost of telegrams, many commercial code books were published so that long phrases could be reduced to one group, resulting in the savings of millions of dollars for businesses that did business by telegram. For instance, one of the most popular codes, The ABC Universal Commercial Electric Telegraphic Code, (commonly, the ABC Code) encoded the whole sentence "Will have an examination soon as possible" as one code group, 02115. And 05565 means,  "Store the goods for account of whom it may concern." How much money did this save? Itasca was paying 56 cents per word or group. The ten word sentence above would cost $5.60 which is $89.60 in 2011 dollars. But replace it with its code equivalent, 05565, and it only cost $0.56, $8.96 today. Cables cost so much that it was worth it to businesses to hire full time code clerks who's only job was to encode and decode telegrams all day long using code books such as the ABC Code. This was much less expensive than paying for the full length telegrams.

The same goes for weather reports. I have attached a radiogram from the Swan and a marked up version showing the decode of the six standard code groups.  I am also attaching the complete code book.
gl
« Last Edit: January 22, 2012, 12:10:03 PM by Gary LaPook »
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Harry Howe, Jr.

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Re: Deciphering coded radiograms
« Reply #1 on: January 23, 2012, 01:31:16 PM »


Sheila
Interesting bit about radiograms prior to the development of "Morse Code", words were given numbers that were then published in Code Books and distributed to operators, and messages were coded and decoded using the numbers in those code books.

Then a guy named Alfred Vail came along and developed a use distribution of the lettera of the alphabet and with Morse they developed the Morse Code.
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Gary LaPook

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Re: Deciphering coded radiograms
« Reply #2 on: January 24, 2012, 04:29:40 PM »


Sheila
Interesting bit about radiograms prior to the development of "Morse Code", words were given numbers that were then published in Code Books and distributed to operators, and messages were coded and decoded using the numbers in those code books.

Then a guy named Alfred Vail came along and developed a use distribution of the lettera of the alphabet and with Morse they developed the Morse Code.
These codes were developed after the development of the Morse telegraph, there was no need prior. These codes had both numbers and code words to represent each phrase or word. These are the examples I gave earlier:

"The ABC Universal Commercial Electric Telegraphic Code, (commonly, the ABC Code) encoded the whole sentence "Will have an examination soon as possible" as one code group, 02115. And 05565 means,  "Store the goods for account of whom it may concern." How much money did this save? Itasca was paying 56 cents per word or group. The ten word sentence above would cost $5.60 which is $89.60 in 2011 dollars. But replace it with its code equivalent, 05565, and it was only $0.56, $8.96 in today's dollars."

For the first phrase you could use either 02115 or "essayist" and for the second, either 05565 or "spunger." I suspect that the words were used more often. The reason that the number equivalents were provided is that you could add a level of secrecy by adding a secret key number to each group, say 12345, with non-carrying addition, e.g. 02115 + 12345  = 14450. The receiver of you message would then subtract the same secret key number, 14450 - 12345  = 02115, and then look up the phrase in the code book. You could have a bunch of key numbers, used in sequence, making it harder for anyone, not the intended recipient, to decipher. This was important with business competition, your competitor could undercut your bid if he could find out what it was. This is what is called an "enciphered code"  and  was used by all military powers such as Japan's well known JN 25 code used to send Naval messages about the attacks on Pearl Harbor and Midway Island. JN 25 had thousands of additive key groups making cracking that code extremely difficult.

gl

« Last Edit: January 24, 2012, 04:33:15 PM by Gary LaPook »
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