Exploded view of an Enigma rotor.
The Enigma was a small, portable electro-mechanical rotor machine used to encrypt and decrypt secret messages.
Key: (1) notched ring; (2) marking dot for "A" contact; (3) alphabet tyre; (4) plate contacts; (5) wire connections; (6) pin contacts; (7) spring-loaded ring adjusting lever; (8) hub; (9) finger wheel; (10) ratchetPhoto credit: Eric Pierce