The Tefifon Grooved-Tape Recorder

The ‘Tefifon’ was originally developed by Dr Karl Daniel in Germany in the 1930s as an answering machine. It used a flexible endless tape loop with parallel grooves that were read (electro-) mechanically. In contrast to later models, this unit was also capable of recording. The project, however, failed to meet the stringent requirements of the German post and telegraph administration.