Charles Judge Mitchell. Mitchell’s Self-Testing Safety Code (1906 and revised edition, 1906/07)
A comparision of my photocopies of the two editions doesn’t reveal any differences in format. Will have to investigate further.
151pp, BL (which dates this 1907) General Reference Collection 8758.e.31
Mitchell’s Self-testing Safety Code. A New and Scientific System for the Transmission of Messages by Telegraph or Cable, so arranged that one word may convey several meanings, such as Article, Quality, Price, Quantity, Terms, etc., thus saving the user 50 and oft-times 75% of the ordinary charges.
147pp, BL (which dates this 1907) General Reference Collection 8758.e.33
Mitchell’s Self-Testing Safety Code, Revised Edition. A new and Scientific System for the Transmission of Messages by Telegraph or Cable, so arranged that one word may convey several meanings, such as Article, Quality, Price, Quantity, Terms, etc. / By other codes three and four words are required to express what this system will convey in One word, thus costing three and four times as much as the same message if sent by this system.
This revised and enlarged edition must not be used with the former issue of Mitchell’s Self-Testing Safety Code, which is now out of print.
In both editions, the
self-testing feature involves the initial letters of the cypher components in columns of each table; the entire code consists of tables, forming 10L codewords. Assembly of some codewords involves use of multiple tables, e.g.,
first three letters for selection from commodities list (table), followed by
two letters for another specification (e.g., paper in tables 414-417), followed by
five letters from another table (101/4) for cost, dimensions, etc.
Mitchell attempts to introduce to a general commercial code, features that might better work for a private, specialized code. It seeks (1) to encompass all topics in tables; (2) to be an alternative to figure codes; and (3) to incorporate its own check system within each 10L codeword. His prefaces are promotional, suggesting that his is aiming for a more general (and perhaps less sophisticated) market.
Aside: Around this time, so-called three-letter codes made their appearance; these had the same general aims, involving the assembly of a 10L codeword from 3 + 3 + ciphers, followed by a check number.
|page 93, from poor photocopy of revised edition.|
Mitchell’s check system was patented; see US 831,968 for a Self-Testing Safety Code (1906, CCL 283/17). The drawing is shown below.
|drawing, from US831,968 Self-Testing Safety Code (1906)|
The specification provides the following explanation of the system, referring to the table in the drawing —
Messages are sent by extracting from the columns of meanings the message desired and writing as a single word the symbols found opposite said meanings. The receiver of a word or words so constructed refers to his copy of the table or section of the code and applies his tests to the word or words before attempting to decipher the meaning. In this case, the receiver confirms that ten letters are present, and then proceeds with the second test, to see
whether the predetermined letters or vowels occur in their predetermined position. This practically gives for the table in question three tests. For instance, the second letter must be the vowel
E, the seventh the vowel
I, and the last letter a consonant. If the word received stands all these tests, the chances are in favor of the message being correct. It will be found that by means of this system of tests at least fifty per cent. of possible errors in transmission will be detected and can be corrected on the spot without reference to the sender. With ordinary codes no such correction is possible...
The table shown below is taken from the earlier (non-revised) edition —
|p66 (cropped, from photocopy), Mitchell’s Self-testing Safety Code (Toronto, 1905)|
The table shown above provides instructions for marking goods and packages. Style — whether of diamond or triangle or circle — is not at issue. Other codes (the Cotton Telegraph Code of Meyer comes to mind) also provide descriptions of / instructions for marking goods; I view these as a kind of ekphrastic code: pictures into words.
Charles Judge Mitchell (1851-1912, d. Kingston, Ont).