Tour guide system including means for noise and crosstalk suppression
First Claim
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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Accused Products
Abstract
An electronic tour guide system including means for suppressing objectionable crosstalk and noise is described. Crosstalk suppression is achieved by means of a comprssor in the transmitter and an expander in the receiver. Objectionable noise between loops is eliminated by means of a squelch circuit which reduces power drain whenever the received signal is below a certain threshold. The transmitter and receiver are designed to handle a plurality of information signals simultaneously. For example, a listener can select one of several different languages broadcast within an antenna loop. The transmitting loop antenna is matched in impedance to the output of the channel means in the transmitter so that maximum power transfer is obtained. Each receiver is further equipped with a gravity operated mercury switch which turns off power to the receiver when the receiver chasis is inverted. It is anticipated that this system will find application in museums, art galleries, archeological sites and the like where it is desirable to guide people from location to location and to address them in their respective languages.
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Citations
10 Claims
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1. An improved, low power, multi-channel tour guide system comprising:
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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, and at 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 wherein said 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, and an 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 including an acoustical transducer means connected to the output of said expander means.
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2. An improved, low power, multi-channel tour guide system comprising:
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a transmitter including; a recording means, at least one channel means and a closed loop transmitting antenna, each channel means comprising; an electronic compressor connected to said recording means, an oscillator means, a modulator means connected to said oscillator means and to said compressor, and a coupling means for connecting said channel means to said closed loop transmitting antenna, and at least 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, and an acoustical transducer means connected to the output of said expander means, said expander means further comprising; 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 wherein said 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, said variable resistance means comprising a first and second field effect transistor with gates coupled together and with their cources and drains connected in series, said series combination of both having an expansion limiting resistance in shunt therewith, and wherein the gate of said first field effect transistor is connected to the output of said first branch and the gate of said second field effect transistor is connected to the output of said second branch, and an 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 said 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. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10)
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Specification