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uk.telecom.voip (UK VOIP) (uk.telecom.voip) Discussion of topics relevant to packet based voice technologies including Voice over IP (VoIP), Fax over IP (FoIP), Voice over Frame Relay (VoFR), Voice over Broadband (VoB) and Voice on the Net (VoN) as well as service providers, hardware and software for use with these technologies. Advertising is not allowed.

Asterisk - less PSTN echo via XP100 clone or ATA?



 
 
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  #1  
Old November 15th 05, 03:35 PM posted to uk.telecom.voip
Matt
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Posts: 141
Default Asterisk - less PSTN echo via XP100 clone or ATA?

Hi,

As the subject says, which of the above shold give me less echo on PSTN
calls?

Many thanks

Matthew

  #2  
Old November 15th 05, 03:36 PM posted to uk.telecom.voip
Matt
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Posts: 141
Default Asterisk - less PSTN echo via XP100 clone or ATA?

Sorry shold = should.

Must use prevew option more...

  #3  
Old November 15th 05, 06:43 PM posted to uk.telecom.voip
Jono
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Posts: 209
Default Asterisk - less PSTN echo via XP100 clone or ATA?



Matt wrote:
|| Sorry shold = should.
||
|| Must use prevew option more...

or preview, even?


  #4  
Old November 15th 05, 06:47 PM posted to uk.telecom.voip
Jono
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Posts: 209
Default Asterisk - less PSTN echo via XP100 clone or ATA?



Matt wrote:
|| Hi,
||
|| As the subject says, which of the above shold give me less echo on PSTN
|| calls?
||
|| Many thanks
||
|| Matthew

I wouldn't use the XP100 clone for anything other than testing. the call
quality is poor. (Lots of clipping seems to occur, at least for me anyway)

My SPA3000, acting as a SIP trunk, gives me much more flexibility and the
sound quality is great. Obviously, with [email protected], the ZAP (XP100)
channels can receive faxes & forward them by email. I've not sussed out how
to do that yet, with a SIP channel.





  #5  
Old November 15th 05, 06:58 PM posted to uk.telecom.voip
Matt
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Posts: 141
Default Asterisk - less PSTN echo via XP100 clone or ATA?

Ooops. I'll blame that on the 3 hours sleep last night, caused by a
teething 1 yr old.

Matthew

  #6  
Old November 16th 05, 10:18 PM posted to uk.telecom.voip
PeterW
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Posts: 49
Default Asterisk - less PSTN echo via XP100 clone or ATA?

"Matt" wrote in
ups.com:

Hi,

As the subject says, which of the above shold give me less echo on PSTN
calls?

Many thanks

Matthew


The main problem with the X100P clone is impedance matching. Most seem to
be 600ohm US standard. In the UK this gives a lot of echo when the device
tries to transmit to the phone line. The proper Digium card had more
configurable impedance matching.

Peter
  #7  
Old November 17th 05, 01:18 PM posted to uk.telecom.voip
Sparks
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Posts: 156
Default Asterisk - less PSTN echo via XP100 clone or ATA?


The main problem with the X100P clone is impedance matching. Most seem to
be 600ohm US standard. In the UK this gives a lot of echo when the device
tries to transmit to the phone line. The proper Digium card had more
configurable impedance matching.

Peter


Would changing a resistor on the card be an option here?

Sparks...


  #8  
Old November 17th 05, 08:08 PM posted to uk.telecom.voip
Matt
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Posts: 141
Default Asterisk - less PSTN echo via XP100 clone or ATA?

If we knew which resistor, i'd give it a try!

Matt

  #9  
Old November 17th 05, 10:52 PM posted to uk.telecom.voip
alexd
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Posts: 331
Default Asterisk - less PSTN echo via XP100 clone or ATA?

Matt wrote:

If we knew which resistor, i'd give it a try!


Perhaps you could cheat, and put the resistance across/in series with the
line?

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  #10  
Old November 18th 05, 09:56 PM posted to uk.telecom.voip
PeterW
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Posts: 49
Default Asterisk - less PSTN echo via XP100 clone or ATA?

alexd wrote in :

Matt wrote:

If we knew which resistor, i'd give it a try!


Perhaps you could cheat, and put the resistance across/in series with the
line?


The BT line and phone have a complex impedance (resistance/capacitance).
See http://www.sinet.bt.com/355v1p5.pdf

The phone terminal impedance is 370 ohm + 620 ohm || 310nf. The network
input impedance is 300 ohm + 1000 ohm || 220nf.

I believe that UK networks are designed as 600ohm. I am not sure of how to
match the two properly. It should be possible with the appropriate circuit,
but I'm afraid I have forgotten my circuit theory. The problem seems to be
mainly with echo being reflected back to the phone (ie X100P clone card)
when it transmits to the line. It seems less noticeable the other way
round.

Maybe there is a good telecoms engineer out there who could come up with a
matching circuit which could go between the card and the phone socket as
part of the interconnecting cable?

Peter
 




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