[Asterisk-Users] ADIT 600 "Dynamic Impedance matching"

[Matt Schulte]

Thanks for the response, it's a rather simple setup. What worries me is
we're going into an old PBX, the channelbank goes 25pair about 20 feet
to a punchdown block. Then from the block goes to another block
(standard telco room layout) then to the phone system. The old phone
system is a Meridian, about 20 years old. All the phones coming off that
are analog from what I gather, the building wiring can range from 5 - 50
years old. 

What's unusual is I've never heard this echo personally. I've had the
customer call from different phones of course and I've dialed out from
these phones to even my cell phone and haven't had a problem. What's odd
is this seems to be random, if I could get it to happen everytime on a
single phone then I could point fingers at the internal wiring. shrug,
else all I have to blame is the cb or the wiring between it and the pbx.

Thoughts?

-----Original Message-----
From: Andrew Kohlsmith [mailto:akohlsmith-asterisk at benshaw.com] 
Sent: Wednesday, March 23, 2005 8:31 AM

On March 23, 2005 08:25 am, Matt Schulte wrote:
> Has anyone ever heard of this so called Dynamic Impedance matching on 
> the ADIT 600? I called their support and they've never heard of it. We

That's odd, I have always had excellent support from CAC.  And FWIW I've
never 
had echo problems with their channel banks.  Ever.  I have echocancel
turned 
off in the Zapata driver.

> The only clue to the dynamic impedance is that the 5g and ver8 of the 
> FXS cards can "hardcode" the impedance according to country. Well 
> that's fine and dandy but so can a Rhino CB-24 in the rating of 
> milliamps..

You don't tune impedance in milliAmps.  That's a current measurement.
The 
Rhino can probably alter the amount of current it can source and this is
what 
they're talking about.  Not having used Rhino's stuff, I can't say for 
certain, but you simply don't alter impedance by changing mA.

(yes, IAAEE).

> Does anyone have suggestions regarding these issues? Please hold back 
> the flaming comments. I'm not here to flame, but to resolve and very 
> tiring issue. :-)

You can start by giving us a connection diagram between the Adit600 and 
whatever you're hooked up to, including grade of cable, how long it is,
what 
it's terminating to (make and model) and whether you've tried replacing
some 
runs with other cable to test.

Invariably my Adit600 analogue runs are always under 50 feet since I'm 
terminating to a PBX or KSU nearby.  These devices are able to terminate
very 
long (km) runs, so I am curious as to why you're having such issues.  Do
you 
have the gains on the Adit600 or Zapata turned way up?

-A.
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