Internal Setting of M-209

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M-209 Workings Home Page M-209 Workgins: 		[Exerpt from M-209 Manuals, additions by author are enclosed by brackets {},]

Introduction

Before enciphering or deciphering a message, the code clerk must set the Internal key of the M-209.

The internal key is composed by the pins and lugs setting. This setting is made in accordance with a cipher-key list. Each code clerk of the same key-net (a division for example) shares the same key list which was prepared by the signal officers of the military unit. Normally, a key list is valid for one day. The key lists of the month are usually written in a document named SOI (Signal Operation Instructions). In the following example, we use the key list included in the TM 11-380 manual of 1944.

Key List

Position of key wheels pins
Wheel 1 (26):   AB_D___HI_K_MN____ST_VW___
Wheel 2 (25):   A__DE_G__JKL__O__RS_U_X__
Wheel 3 (23):   AB____GH_J_LMN___RSTU_X
Wheel 4 (21):   __C_EF_HI___MN_P__STU
Wheel 5 (19):   _B_DEF_HI___MN_P__S
Wheel 6 (17):   AB_D___H__K__NO_Q

Position of drum bar lugs
1.  3-6		10.  2-0		19.  2-0
2.  0-6		11.  2-0		20.  2-5
3.  1-6		12.  2-0		21.  2-5
4.  1-5		13.  2-0		22.  0-5
5.  4-5		14.  2-0		23.  0-5
6.  0-4		15.  2-0		24.  0-5
7.  0-4		16.  2-0		25.  0-5
8.  0-4		17.  2-0		26.  0-5
9.  0-4		18.  2-0		27.  0-5 

26-letter check
TNJUW  AUQTK CZKNU TOTBC WARMI O
pins lugs 26 letters
Set a Pin Set a Lug 26 letters check

Setting Wheel Pins

Open the outer cover of the converter, and raise the inner lid. If the machine has been properly zeroized (see later in this chapter), all of the key wheel pins will project from the left-hand side of the key wheels. If any project from right-hand side, use the screw driver provided and push them to the left. This will make the setting easier.

Set the pins in accordance of the key list. The colums of letters and dashes represent the six key wheels, from left to right {in the example above, each wheel setting isn't represented vertically, but horizontally}

The pins associated with the letters which are printed in the colums {in the rows in the example above} are to be pushed to the right, or effective position. Where a dash appears, the pin associated with the ommitted letter will remain at the left, or ineffective position. Thus, following the exemple, the pin under letter A on wheel number 1 {wheel with 26 letters} should be moved to the right or effective position. The pin under letter C on wheel number 1 will remain at the left, or ineffective position. A knife blade or the special screw driver provided may be used to set the pins...

Setting Lugs

With the inner lid open, the drum will be seen in the rear of the machine. Each of the 27 drum bars has 2 movable lugs which may be placed in effective positions 1 through 6, or in 2 noneffective positions labeled "0".

Consult the key list. The 2 colums of number represent the 27 drum bars. The numbers opposite each drum bar number denote the positions which the two lugs on each drum bar will occupy...

For example, on bar 1, the left-hand lug will be moved to position 3 and the righ-hand lug to position 6. On bar 2, the left-hand lug will be moved to the left zero position, and the right-hand to position 6.

Turn the setting knob to release the drum lock to allow the drive knob to rotate the drum. Use the special screw driver provided to move the lugs from one position to another. When correctly placed, each lug will lock in position in a small hole. When moving a lug, push it slightly toward the front of the machine to release it, before attempting to slide it to another position....

Twenty-six-letter Check

Every cipher-key list will include a 26-letter check. Using this check, the operator of Converter may verify his preliminary settings...
  1. Set the encipher-decipher knob in the C position.
  2. Set the initial alignment of AAAAAA on the key wheels by turning them individually until the letter A of each wheel lines up the white bench mark.
  3. Turn the indicating disk until the letter A is on line with the indicating index.
  4. Encipher by operating the drive knob.
  5. Continue the encipherment of "A's" in the same manner until the letter counter shows that 26 letters have been enciphered....
  6. Compare the tape with the 26-letter check in the cipher-key list. If the tape and the 26-letter check are identical, the pin and lug settings are correct...

Zeroizing the machine

When the converter is closed at the end of a day or a period of operation, the internal keying elements of the device must be zeroized. First, push all of the key wheel pins to the left or ineffective position. Second, move all lugs to the zero posistions on the drum bars. Tear off any tape which contains printing, and close the outer cover of the machine ...

decipher action tapes

Duration of traitements

I timed the keying time:
  • Zeroizing the cipher machine: 5 minutes
  • Perform Pins setting: 8 minutes
  • Perform Lugs setting: 8 minutes
  • Perform 26-letters check: 5 minutes
In all: 26 minutes (about 1/2 hour).

References