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Automatic channel switching from fallback channels to regular channels

  • US 5,138,609 A
  • Filed: 12/20/1989
  • Issued: 08/11/1992
  • Est. Priority Date: 12/20/1988
  • Status: Expired due to Fees
First Claim
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1. A channel switching system for normally interconnecting first and second stations through first and second regular channels and interconnecting said stations through fallback channels established by a public switched telecommunications network in the event of a fault in said regular channels, comprising:

  • first tone generator means for transmitting a first tone signal from said first station to said second station through said first regular channel in the event of said fault;

    first signal-to-noise detector means for receiving said first tone signal at said second station, deriving a signal-to-noise ratio of said first regular channel from the received tone signal, and transmitting a quality signal indicative of the signal-to-noise ratio of the first regular channel to said first station;

    first switching control means for receiving said quality signal at said first station and determining whether the signal-to-noise ratio of said first regular channel represented by the received quality signal is higher than a reference value, and switching the first station from said fallback channels to said regular channels if said signal-to-noise ratio is higher than the reference value;

    second tone generator means for transmitting a second tone signal from said second station to said first station through said second regular channel when the signal-to-noise ratio is determined by the first switching control means as being higher than said reference value;

    second signal-to-noise detector means for receiving said second tone signal at said first station and deriving a signal-to-noise ratio of said second regular channel from the received tone signal; and

    second switching control means for determining whether the signal-to-noise ratio of said second regular channel is higher than said reference value and switching said second station from said fallback channels to said regular channels if the signal-to-noise ratio of the second regular channel is higher than the reference value.

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