The Abwehr Enigma

The Abwehr Enigma machine differed from the Army and Navy models, in that the mechanism that stepped the rotors used a different approach. (All images courtesy of David Hamer, whose site is located at: http://www.eclipse.net/~dhamer/). The machine had a serious design flaw. Frequently all four wheels turned at once, which the codebreakers termed a "Lobster". When this occurred, the scrambler assembly stayed in the same configuration, except shifted by one position.

Click on the thumbnails to enlarge images.

The machine, cover open. The rotary switch on the right has three positions: Battery, Off, and External Accumulator (battery). Two terminals on the right side are for connecting to an external battery. Note that there is no Stecker (plug) board. (134K)

The keyboard. Note the difference from the Standard Enigma. Each key is marked with two sets of characters. (68K)

Cover raised, showing the scrambler in place. Note that there are four rotors, as with the Naval Enigma, except that all four move, unlike in the Naval version. (135K)

Close-up of the scrambler. (144K)

Cover open, scrambler removed, showing stepping mechanism. (140K)

The Eintrittwalze (entry "rotor"). Strangely, in view of the complexity of the machine, the diagonal of the entry rotor is QWERTZU... The indicator bulbs operate at 4 volts. Although the lamp base is essentially the same as the modern flashlight bulb, the glass envelope is flatter. It is extremely difficult to find replacement bulbs, as modern day flashlight bulbs are too high to fit in the machine. (132K)

Scrambler assembly. (55K)

"Plate" side of rotor, with notches. The rotors are smaller (8.5 cm.) than for the standard Service Enigma (10 cm.). (41K)

"Pin" side of rotor, with stepping gear. (40K)

Umkehrwalze ("turn-around" rotor), with advancing mechanism including stepping lever, gears and pinions. (128K)

Reference

Hamer, David H. "G-312: An Abwehr Enigma", Cryptologia, XXIV, Number 1, pp 41-54.

Last updated 12/7/00