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Method and circuit arrangement for adjusting the volume in a mobile telephone

  • US 5,313,661 A
  • Filed: 01/31/1990
  • Issued: 05/17/1994
  • Est. Priority Date: 02/10/1989
  • Status: Expired due to Term
First Claim
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1. Method for user adjustment of the volume of a mobile telephone including a transceiver unit and a physically separated operating device, comprising the steps of:

  • manually adjusting a dc voltage level of said telephone to provide a desired volume using circuit means in the operating device, said voltage level being variable in a preselected voltage range,supplying a control signal corresponding to the dc voltage level to a microprocessor,reading the control signal with the microprocessor,adjusting the volume in relation to the control signal by controlling the gain of an audio amplifier through a multiplexer connected to the microprocessor, said multiplexer selecting an impedance connected in series with an input impedance of said audio amplifier.

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