[Asterisk-Dev] Re: How to measure delay in meetme?

[Clive Nicolson]

On Wed, 31 Aug 2005, Steve Edwards wrote:

> Thanks for the reply. I thought about a solution similar to yours, but 
> rejected it because of a lack of resources -- primarily access to an 
> oscilloscope.

What I described can all be done (by analogy) with audio software on a pc.

> 
> I came up with a cheaper and easier solution.
> 
> Radio Shack/Tandy sells a "Telephone Recording Control" (P/N 43-22BA, 
> US$25.99).
> 
> This little black box has an RJ11 jack, an RJ11 plug, an 1/8" mono plug, 
> and some sort of plug to control a tape recorder.
> 
> I connected the "TRCs" to 2 POTS phones and plugged the mono plugs into a 
> "mono to stereo adapter" (P/N 274-375, US$4.99). I plugged the adapter 
> into the line in jack on my laptop.
> 
> Using Audacity (http://audacity.sourceforge.net), I can record both phones 
> as left and right.
> 
> I muted 1 phone to make sure I wasn't recording sound from its mic.
> 
> By tapping the other handset on the table, Audacity can measure the 
> interval between the 2 "pips."

=================
And the delay is?
=================

> 
> On Thu, 1 Sep 2005, Clive Nicolson wrote:
> 
> > On Mon, 29 Aug 2005, Steve Edwards wrote:
> >
> >> On Mon, 29 Aug 2005, Tony Mountifield wrote:
> >>
> >>> I've never found problems with delay when only Zap channels are involved;
> >>
> >> Personally, I don't think anybody would notice in a real conversation, but
> >> you can notice it if you have a separate phone to each ear or if you
> >> listen on one handset and tap the table with the other.
> >
> > Get a dual channel oscilloscope, a audio signal generator, a small speaker
> > and a microphone. Set the generator to a frequency lower that the delay you
> > think you are hearing. Feed the signal to the speaker and one channel of
> > the scope (trigger of this signal), adjust the level so you can hear it.
> > Connect the microphone to the other scope's other channel and place the
> > microphone near the speaker. Adjust the gain on that channel so that you
> > can compare the 2 undelayed signals.
> >
> > Now place the speaker near the mouth piece of one phone and the microphone
> > near the ear piece of other phone. Establish a call between these phones.
> >
> > You should be able to measure the delay over that path on the scope!
> >
> > Borrow the scope and signal generator and get the speaker and microphone
> > from Tandies (your local electronics store).
> >
> > Clive
> >
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> 
> Thanks in advance,
> ------------------------------------------------------------------------
> Steve Edwards      sedwards at sedwards.com      Voice: +1-760-468-3867 PST
> Newline           pagesteve at sedwards.com            Fax: +1-760-731-3000
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