SHOWCASE 7L. CELL 7-13

The idea of using telephone lines to deliver Long Wave radio signals (150-300 kHz) was explored in Germany since 1924. The early system called "NF-Drahtfunk" allowed to listen to just one program which would be interrupted every time when external phone calls arrived. 

Starting March, 1939, the "HF-Drahtfunk" was implemented to allow for up to three different broadcast programs to be received over a telephone line on top of regular phone calls. There were three standard frequencies in Long Wave band chosen for "HF-Drahtfunk" - 160, 210 and 249 kHz. 

Each German citizen could buy special splitting and switching modules to install them at home and have a choice of either regular radio or Wired Broadcast. The idea proved to be especially useful by the last years of WW II when air raids of English and American bombers to Germany became quite frequent (Bombenkrieg) and German broadcast radio stations would suspend their on-the-air transmissions not to serve beacons for the approaching bombers. Under such circumstances, only those civilians who had "HF-Drahtfunk" installed in their homes could receive timely warnings about expected air attacks. 

The HF-Drahtfunk networks remained in use in Germany till mid-1963 and in Swiss up to late 1990s (!!)

Our appreciation to Prof. Dr. Otto Kunzel for sharing and correcting the above Drahtfunk information.