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Method and device for increasing the security against transmission errors in an information transmission system

  • US 4,138,676 A
  • Filed: 03/11/1977
  • Issued: 02/06/1979
  • Est. Priority Date: 03/26/1976
  • Status: Expired due to Term
First Claim
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1. In a device, particularly for the railroad field, for increasing security with respect to transmission faults in an information-transmission system, in which an interrogation device and a passive response device are movable relative to one another, and in which the interrogation device transmits an interrogation signal which can be periodically swept through a predetermined frequency band, preferably in the microwave range;

  • the said interrogation device receiving as a response signal, from the passive response device, during a read operation of at least two periods a frequency selectively reflected interrogation signal in accordance with a k-digit information item to be transmitted;

    the said interrogation device being provided with at least two memories, one of which receives the currently obtained information item, and the other of which receives a previously obtained information item;

    the said interrogation device being provided with a code and/or identity checking device, which after each period of the response signal assigns an error designation value showing how many of the digits are incorrect;

    the said code and/or identity checking device being connected with at least two memories, one of which receives the current error designation value, and the other of which receives the lowest previous error designation value;

    the said interrogation device being provided with a comparator which compares the current and the lowest previous error designation value and closes switching means, which transfers the content of the memory with the currently obtained information item to the memory for the previously obtained information item, if the current error designation value is lower than the lowest previous error designation value, the combination of means for determining the input level of low frequency portions lying below the sweep frequency of the interrogation signal of the response signal;

    means for comparing the input signal level of the currently received period of the response signal with the input signal level of the previously received period of the response signal, operative to deliver a first signal to said switching means if the input signal level of the currently received period is higher than the input signal level of the previously received signal;

    said comparator, comparing the current and previous error designation values being operative to deliver a second signal to said switching means if both values are equal;

    closing of said switching means taking place in the simultaneous presence of both of said first and the second signals.

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