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Converting phone handset audio to PC soundcard line-in audio

Discussion in 'Electronic Basics' started by Isaac Grover, Jul 16, 2004.

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  1. Isaac Grover

    Isaac Grover Guest

    Hi everyone,

    I have been recording weekly conference calls since January, and I'm
    looking to upgrade the quality of my recordings. Currently, I'm
    connecting my cordless phone to the line-in jack on my PC's soundcard
    with a 6' audio cable.

    I would like to take the audio from a landline telephone, so I tore
    apart the handset on my wired phone to see which wires connected the
    handset's speaker to the base. I saw that it was pins 2 and 3 (top
    left and bottom right), so I connected pin 2 (green) on the handset
    jack to ground on a spliced audio cable, and connected pin 3 (red) on
    the handset jack to tip on the audio cable.

    I can hear the audio from the phone line, but not without problems.
    There is an intrusive hum that almost drowns the phone line audio, and
    whenever pin 2 (green) is connected to ground on the audio cable, my
    wired phone's base takes the line off-hook, even if the handset is
    still on the cradle.

    So can someone tell me how to eradicate the hum, and how to keep the
    line on-hook if I am not using my "high-tech" conversion device?


    Do you make $100,000 per year? Do you work from home?
    Do you want to?
  2. Rich Grise

    Rich Grise Guest

    Use two capacitors. Measure all your polarities, and use about
    100-220 uF caps at at least 250V. These will be electrolytics, which
    is why you need to know the polarities. This will isolate them, unload
    the phone line, and not ground the telco's system.
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