Browse Prior Art Database

Method for Multiplexing a Headphone Out and a Line Out by Single Audio Jack

IP.com Disclosure Number: IPCOM000123002D
Original Publication Date: 1998-Mar-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 37K

Publishing Venue

IBM

Related People

Fujii, K: AUTHOR

Abstract

A circuit is disclosed that a headphone out and a line out can be supported by single output jack in an audio circuit of a mobile PC (Personal Computer).

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Method for Multiplexing a Headphone Out and a Line Out by Single
Audio Jack

      A circuit is disclosed that a headphone out and a line out can
be supported by single output jack in an audio circuit of a mobile PC
(Personal Computer).

      In a desktop PC environment, it is common that an audio circuit
board has two output jack.  One is for a headphone and another is for
a line out.  The headphone out jack is used to hear the computer
sound by  headphone.  To get the highest audio quality output, for
example to connect the PC to a external Hi-Fi audio amplifier, the
line out jack is used.  On the other hand, in a mobile PC
environment, it is very difficult to have both of those output jack.
It is because available space is limited.  Most of the mobile PC has
only headphone jack. Those  mobile PC users can not get the highest
quality audio output which can  be got from line out jack in desktop
case.

      By the circuit disclosed, the headphone out and the line out
are multiplexed by single jack.  User can select one of those two
output by means of a specific software.  Fig. 1 shows the structure
of this circuit.  When the line output is selected, a headphone
amplifier circuit  is bypassed and an audio out from the audio
controller is connected to  the output jack directly.  The analog
switches are controlled by the "+Line out Enable" signal.  This
signal is controlled by a specific software.