I would like to adapt audio level on a phone line to a computer microphone input. I assume the microphone sensitivity is roughly the same among computer sound cards. In North America (correct me if I'm wrong), the phone line level is -10dBm (or dBu, I'm a bit confused here...), this should translate to 77.5mVrms into 600 ohms.
How much attenuation should I use to connect to a microphone input?
Dan
--DF
In article , snipped-for-privacy@def.net (known to some as D. G.) scribed...
You would do well to consider that most phone companies are still picky about what gets hooked up to their lines, and that ringing voltage is on the order of 90-100VAC at 20Hz, and get yourself a proper voice coupler. Such a device will protect you and your equipment.
Have a look at this page:
Happy hunting.
It seems the full signal or may be half of it is fed into the microphone input in this design. Strange! I would fear it can overload the input or be more compatible with a LINE level input... Coincidence, what I'm building is for the same purpose (for VoIP) but I use a 600 ohm transfo for the hybrid circuit. The design at
Dan
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BTW -10dBm translates to 245 mVrms into 600 ohms: 10*log10(PmW/1mW)
--DF
Oops! I was using 20*log() equation.
Thanks for the link at
Regards! Dan
Another simple solution
RS232 solution is
I fear you have posted an incorrect link. What has IRMeasure to do with adapting a phone line to a computer sound card input?
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