[Asterisk-Users] Echo Cancellation Feature

[Rich Adamson]

> <snip>
> 
> I've got a fair amount of test equipment (and 20+ years telephony 
> background), and am planning to assemble a document identifying some of 
> the pstn issues, level settings, and other things impacting a reasonable
> 
> system implementation. Unless someone wants to UPS a transmission test 
> set to me quickly, the document won't be completed for several weeks. 
> (The only test set I have access to will not be released for a couple 
> of weeks due to classes, etc.)
> 
> I'm also expecting these tests to point out a number of other
> transmission
> issues within asterisk that we'll get documented with real numbers, etc.

<snip>

> One suggestion I would like to make, is where possible, tell us how to
> replicate the tests as best we can if we don't have the proper
> equipment.  I'd venture to say most of us have a good, fairly sensitive,
> digital VOM.  I know not all tests can be made with that, but I'm sure
> some of them can.
> 
> There are fairly accurate tone generator programs that work with a sound
> card, same with data decoding.  My point is, as you said before, not
> everyone has a multi-thousand dollar test set, but would still like to
> do what they can to properly implement a telephone system.

I'm about 95% confident I can measure and describe several different
issues that truly have been impacting interfaces to pstn lines, etc.
But, I need to validate the steps before running off at the mouth with
misrepresentations, etc. I don't believe these issues are asterisk
related at all, but rather outside influences that many are feeling
but can't see (or deal with).

Assuming I'm correct, the instrument needed to identify at least "some"
of these issues retails for about $300 US. Example, www.triplett.com
click on Test Equipment, Telco Testers, Model 2 to 7, don't know for
sure as yet. Lots of other venders as well. To prove the point (and
write the documentation), several other pieces of test equipment will
be likely for me, but not needed by you. The unit I'm borrowing sells
for over $3,000 but does lots of other stuff not needed in typical
asterisk deployments.

Just about every telephone installer in the US (there are exceptions)
is carrying something similar to the above. They use it to measure levels
"to" the milliwatt generator, and they use the noise measurement side
"to" the quiet termination. The milliwatt generator and quiet termination
are often times implemented in the same piece of telco hardware, but
they have different telephone numbers assigned to them. (Don't think 
we have a quiet termination in asterisk as yet, but should be easy to
implement if it is actually needed.)

The standard VOM isn't going to cut it for these tests as they are no
where near sensitive enough to accurately measure levels, noise, AC
induction, etc. But, if we're all going to play in the telephony 
business then we better buy (and understand how to use) the tools 
necessary to play in that business. I think I can help.

I'm kind of thinking that "if" this can be described accurately, I'd
guess one of the developers can add some code to help measure/identify
the issues. If that impression is correct, then the test set won't be
required at all. Let's see how it goes!

Hopefully I can help that process and understanding even though I'm 
not a coder.

Rich