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

[Steve Edwards]

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.

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."

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