Oliff & Berridge
Medium-frequency radio transmission system
 A medium-frequency radio transmission system is formed by installing a receiving antenna for receiving an amplitude-modulated medium-frequency radio wave at the rooftop of an existing building, receiving the medium-frequency radio wave, coupling the received medium-frequency radio wave to an existing distributing cable or distributing conductive piping with or without a coupler for said radio wave, and transmitting the radio wave to a predetermined floor. At the predetermined floor the basement or tunnel of an existing building such as underground shopping mall, underground parking lot, underground railway, road tunnel or deep space of massive building is provided with a coupling such as an existing loop-like or linear wiring or piping line with or without coupler. 
NHK Integrated Technology Inc. Nippon Hoso Kyokai
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H04B H04H H01Q
inventional inventional inventional
Atsumi Masaaki Tadao Tatehiko Kazumi Shinichi
Fujiwara Kitanda Sugita Toyosawa Shoji Watanabe