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Electronic device accessory

  • US 7,869,608 B2
  • Filed: 09/03/2008
  • Issued: 01/11/2011
  • Est. Priority Date: 01/14/2008
  • Status: Active Grant
First Claim
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1. An accessory that communicates with an electronic device over a wired communications path, comprising:

  • circuitry for transmitting ultrasonic tone signals to the electronic device over the communications path; and

    voltage detection circuitry that responds to direct-current (DC) bias voltages of different magnitudes that are received from the electronic device over the communications path.

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