Codes
The codes were refined and adapted as they were used. By 1867 numerals had been added to the five-needle code. This was achieved through the provision of a sixth wire for common return making it possible to move just a single needle. With the original five wires it was only possible to move the needles in pairs and always in opposite directions since there was no common wire provided. Many more codes are theoretically possible with common return signalling, but not all of them can conveniently be used with a grid indication display. The numerals were worked in by marking them around the edge of the diamond grid. Needles 1 through 5 when energised to the right pointed to numerals 1 through 5 respectively, and to the left numerals 6 through 9 and 0 respectively. Two additional buttons were provided on the telegraph sets to enable the common return to be connected to either the positive or negative terminal of the battery according to the direction it was desired to move the needle.
Also by 1867, codes for Q and Z were added to the one-needle code, but not, apparently, for J. However, codes for Q, Z, and J are marked on the plates of later needle telegraphs, together with six-unit codes for number shift and letter shift . Numerous compound codes were added for operator controls such as wait and repeat. These compounds are similar to the prosigns found in Morse code where the two characters are run together without a character gap. The two-needle number shift and letter shift codes are also compounds, which is the reason they have been written with an overbar.
The codes used for the four-needle telegraph are not known, and none of the equipment has survived. It is not even known which letters were assigned to the twelve possible codes.
Read more about this topic: Cooke And Wheatstone Telegraph
Famous quotes containing the word codes:
“We must trust infinitely to the beneficent necessity which shines through all laws. Human nature expresses itself in them as characteristically as in statues, or songs, or railroads, and an abstract of the codes of nations would be an abstract of the common conscience.”
—Ralph Waldo Emerson (1803–1882)
“... until both employers’ and workers’ groups assume responsibility for chastising their own recalcitrant children, they can vainly bay the moon about “ignorant” and “unfair” public criticism. Moreover, their failure to impose voluntarily upon their own groups codes of decency and honor will result in more and more necessity for government control.”
—Mary Barnett Gilson (1877–?)
“I cannot help thinking that the menace of Hell makes as many devils as the severe penal codes of inhuman humanity make villains.”
—George Gordon Noel Byron (1788–1824)