Sunday, December 28, 2008

Siemens Hell-Feldfernschreiber

A most ingenious way to relay text from one point to another is the Hellschreiber, developed by Rudolf Hell in the 1920's. The Hellschreiber enables readable and error-free communication, even under poor conditions, over radio or land-lines. Text characters are composed by a 7 x 14 matrix and sent as a serialized audio signal to the receiver. The Hell receiver prints out the characters on paper with a unique double winded spindle. It's a simple yet robust system that enables a speed of 150 characters per minute.

The ingenious of the Hell design is how it visually handles error correction and synchronisation problems. The special spindle prints the text twice on the paper ribbon in order to make it readable in all conditions, even when sender and receiver are not fully synchronised.

The Hellschreiber went into service in 1934 and its speed and reliability made it very popular with press agencies and very suitable for diplomatic and military communications. The German Wehrmacht, Luftwaffe and Kriegsmarine used the system from 1935 until 1945 for field operations. Although this beautiful machine has become obsolete due to the introduction of Telex, Fax and e-mail, the device, and even software versions of it, remains popular with radio amateurs.

On Frank Dörenberg's web pages there's a magnificent Hellschreiber page. Frank has composed a detailed historical and technical description of the Hellschreiber. Make sure to visit the 'How it Works' section with its beautiful animated images that demonstrate perfectly how the machine works.

No comments: