German date/time of transmission/serial # (Serial # was allocated when signal was being sent by shore station. A different serial # was given for each radio circuit (eg. Series 1 or 4, etc)) |
Group count (number of four letter cipher groups in original German signal) |
Cipher indicator group showing which cipher was being used ( eg. Triton (Shark) or Bertok) and the group for obtaining message setting (starting position of rotor for that message) |
Allied name assigned to U-boat radio circuit Series’ 1, 2 3, etc. were allied designations for various U-boat radio circuits. The circuits included the Ubootsküstenschaltung (for the Bay of Biscay and the northern approaches to the North Atlantic ), Irland (for U-boats in the north and middle Atlantic ), Amerika (for those in the north western Atlantic, central Atlantic and South American coast), Afrika (for the Indian Ocean ), and Diana and Hubertus. From time to time they were expanded and renamed (eg. Amerika I and II ). |