During World War II, the Germans used a typewriter-like machine named Enigma to encrypt military messages.
It was patented in 1918 by Arthur Scherbius for commercial use, and them adopted by the German Navy 1926, by the Forces in 1928 and by thw Airforce in 1935. It was improved and changed before and during the war, and was used up to the 50s. 100,000 - 200,000 Enigma machines were built.
The dimension of the machine are about 13.5 * 11 * 6 inch. The weight is about 26 lbs. The Enigma is built into a wooden box which can be carried by a single man.
Here is a diagram of it:
Parts of the machine:
From the operator's point of view the machine consists of a keyboard of 26 upper case letters in the pattern of the German typewriter (QWERTZ...).
Above the keyboard is a lamp board with 26 lamps for the 26 letters. The lamps are labeled like the letters.
Above the lamp board is the scrambler unit, consisting of three rotating wheels (also called rotors) on a common spindle (Achse).
On the right side there is a fixed wheel, called entry wheel (Eintrittswalze). On the left side there is a fixed reversing wheel, also called reflector (Umkehrwalze).
The three central wheels are numbered (1-5) and selected from a box of five wheels. The movement of the rotors is done mechanically by key pressing, like with an old typewriter. The wheels move like an odometer (Kilometerzähler). The position of the wheels can be observed by the windows and moved by hand to the ``ground setting'' (Grundstellung).
On the vertical front of the machine there is a plugboard with 26 pairs of sockets (Stecker), labeled again fram A to Z. These sockets can be connected by simple twin cables. With the plugboard you can switch letter pairs.
The machine has an internal battery (4.5 V) and an external adapter. All parts of the machine are wired.