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System for bidirectional data transmission between a plurality of stationary units and a vehicle

  • US 5,444,742 A
  • Filed: 04/28/1993
  • Issued: 08/22/1995
  • Est. Priority Date: 04/28/1992
  • Status: Expired due to Fees
First Claim
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1. A system for bidirectional, electromagnetic transmission of data signals between a plurality of stationary units which have respective effective ranges that at least partially overlap, and a corresponding vehicle unit, wherein the stationary units transmit encoded data signals (ASK) to the vehicle unit (downlink mode), and the vehicle unit transmits encoded data signals (FSK) to the station units by a semi-passive transponder mode, characterized in that at least two stationary units are provided, which operate at predetermined frequency spacings and that in the downlink mode synchronously transmit the same data, and that the reception unit of the vehicle unit is adapted to receive the transmission frequencies of the stationary transmitting units.

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