The permutation code, where combinations of five plus and minus pulses will give thirty-two selective positions, was suggested as far back as 1833 by Gauss and Weber. Whitehouse, in 1854, and Barnett, in 1860, experimented further, using the permutation code to operate a recording mechanism. However, no practical means for actually printing letters and figures was found until 1882 when Jean Maurice Emile Baudot designed a multiplex system to permit the transmission of four messages in each direction over a single line circuit. Later, Baudot designed a tape printer in which the selecting and printing mechanisms comprised an ingenious arrangement of cooperating parts, including a rotating typewheel associated with a coded combiner wheel and five stationary elements selectively movable to received code positions, each element having an extending finger to be brought into contact with the periphery of the coded combiner wheel upon the completion of a selective code setting. When the code combination of the set fingers matched a code on the wheel, a print roller was released to press the recording tape against the typewheel and print the selected letter. Although the Baudot Multiplex was used extensively in Europe, engineers and inventors in the United States had not produced a practical 5-unit permutation-code teleprinter system. They were constantly searching for a unit code system requiring a minimum number of electrical impulses to operate a telegraph printer. Various types of relay systems using distinctive signal pulses were proposed. A three-unit-code system that showed promise, and did not require synchronism, used four different electrical pulse conditions: a high voltage positive or negative pulse, and a low voltage positive or negative pulse. Records show that many inventors played with this code and that John Burry, C. L. Krum, G. A. Cardwell, and J. C. Barclay, among others, built operable equipment using such a code arrangement. The following excerpt from Cardwell’s patent No. 905,497 of December 1, 1908, may be of interest. It describes the code arrangement of four different line conditions in three signal groups to produce 36 different code combinations. In order to energize the controller magnets in proper sequence to position the type wheel for printing a desired letter, a predetermined code or system of sending in the impulses is essential. In an instrument constructed by me in accordance with the present invention I have used the following: