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Tour guide system including means for noise and crosstalk suppression

  • US 3,934,202 A
  • Filed: 03/25/1974
  • Issued: 01/20/1976
  • Est. Priority Date: 03/25/1974
  • Status: Expired due to Term
First Claim
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1. An improved, low power, multi-channel tour guide system comprising:

  • a transmitter including;

    a multi-channel recording means, a plurality of channel means connected to said recording means and a closed loop transmitting antenna coupled to said channel means, andat lease one portable receiver including;

    a receiving antenna,a detector connected to said receiving antenna,an expander having an input and an output terminal, said input terminal being connected to said detector, said expander including an expander amplifier and a feed forward circuit connected to the input terminal of said expander amplifier, said feed forward circuit comprising;

    a first and second branch, each of said branches being in electronic parallel with the other and whereinsaid first branch includes an amplifier means therein and said second branch includes an inverting type amplifier therein,a variable resistance means connected to both of said branches, andan input resistor between said expander amplifier input terminal and said variable resistance means and forming a variable resistance voltage divider network therewith, wherein low amplitude level signals are substantially shunted to ground by the variable resistance means and high amplitude level signals are passed to said expander amplifier whereby higher amplitude level signals are amplified with more gain than lower amplitude signals, said receiver further includingan acoustical transducer means connected to the output of said expander means.

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