Kurier was a burst transmission system for U-boat communications that was first sea trialed by the Kriegsmarine in 1943[1] and subsequently fitted to the Type XXI submarine.
Prior to the opening of World War II, the German Kriegsmarine developed a system known as kurzsignale for sending radio signals from U-boats back to headquarters.
To prevent this, kurzsignale encoded the message into a series of short codes that could be sent by a competent radio operator in about 20 seconds.
Unknown to the Kriegsmarine, Robert Watson-Watt had developed a new system known as huff-duff that could take such measurements in a fraction of a second.
He had originally developed the concept to allow the Met Office to measure the fleeting signals from lightning, and had used it to provide thunderstorm warnings to pilots.
Despite the system being publicly shown, even featured in newsreel films, the concept was largely ignored outside the UK and development continued in secret.
The first prototype was constructed under the direction of Baurat Vollmeyer, a Kriegsmarine official, and test messages were sent from Holzkirchen in southern Germany[a] to Dannau, near Oldenburg on the Baltic coast.
These revealed the previously unseen problem that the electric motor driving the system, taken from a windshield wiper, changed its speed based on the temperature and humidity, which were very different on a U-boat.
The system had a magnetic transducer similar to a tape head positioned over the outer edge of the disk over the bars.
A small box allowed adjustment so that the output of the Geber would match the inputs of the radio found in that U-boat.