M-209 overview

Purpose

a. Converter M-209 is a small, compact, hand-operated tape-printing, mechanical device for rapid enciphering and deciphering of tactical messages.
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It will encipher a plain text message of any length, automatically printing the enciphered text on a paper tape in 5-letter groups; or it will decipher a message that has been previously cryptographed by another Converter M-209, printing the clear text on a paper tape with proper spacing between words {if each space was translated by Z letter during enciphering}.

b. The converter is contained in a metal box, and is normally carried in a canvas case, suspended by a strap over the shoulder. The case has compartments for carrying the manual, pencils, extra tape, message books, and message clips. Inside the cover of the converter are clamps for holding a screw driver, a pair of tweezers, an oil can, an ink pad can, and the roll of paper tape in use. When desired, a hand-carrying strap may be attached to the left side of the machine.

Indentification of parts

a. Preliminary Procedure. Open the outer cover of the machine by pushing the button located in the center of the front of the cover. Raise the inner lid from the front by lifting it off its spring catch.
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Principal operating parts

a. Key Wheel
Letters of the alphabet in normal sequence are engraved on the rims of the six key wheels. On each wheel, from left to right, there is a decreasing number of letters. The letters are arranged on the key wheels as follows:

     Wheel No.    No. Of letters       Letters
       1               26                A-Z
       2               25                A-Z, omitting W
       3               23                A-X, omitting W
       4               21                A-U
       5               19                A-S
       6               17                A-Q
     

Near the rim of the key wheels, and just below each letter, a small pin projects from on side or the other of the key wheels. The key wheel pins may be pushed from side to side in the slots in which they are set.
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The key wheel are mounted on a shaft, ... The key wheels may be turned as a unit in either direction when the reset button is depressed ans the reset knob twisted. Individual wheels may be turned by hand in one direction only.

b. Indicated Disk, c. Reproducing Disk, d. Typewheel
A large knurled knob at the left attached to a metal disk , called the indicating disk, bearing the letters of the alphabet in normal order. The indicating disk is associated with a reproducing disk, one letter of which is visible through aperture. The disk can be rotated freely in either direction, allowing any letter to be aligned on a white bench mark, called the indicating index. The typewheel is mounted on the same shaft with the two disks mentionned above. On its rim ared raised letters for printing.
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The last letter printed and the letter which is read on the reproducing disk are the same.
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j. Drum {named also "Squirrel Cage"}.
When the inner lid is open, the drum can be seen at the rear of the machine. On the drum are 27 drum bars, which occupy about two-thirds of the circumference of the drum and are numbered at the right of the drum. On each drum bar are two movable lugs which may be set in any one of eight positions, numbered:

        	1  ♀  2  3  4  5  ♀  6
     

References

• M-209 Manual : TM 11-380, 1944