unusual telephony request - recording voice mail

[James Knott]

edward.chin-rieW9WUcm8FFJ04o6PK0Fg at public.gmane.org wrote:
> On Mon, 26 Jan 2004 20:20:56 +0200 (IST), Peter L. Peres 
> <plp-ysDPMY98cNQDDBjDh4tngg at public.gmane.org> wrote:
> 
>>
>> On Sun, 25 Jan 2004, Wil McGilvery wrote:
>>
>>> I did not connect to a phone line that is what the phone is for. I
>>> simply rerouted the audio. Inside your phone receiver is a little
>>> speaker. That was what I was talking about. It's the same as plugging in
>>> a headset.
>>
>>
>> No it is not. You were very lucky. Depending on circumstances you could
>> end up with up to 120Vac entering your audio gear (ring voltage).
>>
>> Peter
>> -- 
> 
> 
> In an ordiary handset(phone), line voltage appears at both the
> speaker and mouthpiece (microphone). They are in parallel and would give
> the nastiest feedback if the mouthpiece is anywhere near the speaker.
> The ringing voltage (actually 90vac but still very potent - fatal in some
> cases. I once got zapped doing what you did.)can be avoided by plugging in
> the recording device after connecting, but who needs 48vdc on the mic 
> input?

I guess you've never taken a phone apart.  There is a network that 
connects the handset to the line.  It provides DC blocking for the 
receiver & current limiting to the microphone (for those that still need 
a power source).  Also the mic & receiver are not wired in parallel. 
Doing so would result in excessive "sidetone" level and echo.


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