THL Tone Sweep Method Errors

Unanswered Question
Jul 8th, 2010

Having some echo issues and trying to run THL Tone Sweep on FXO ports. I get the following error: E.

ERL very low. set_impedance to 900r failed !!!.

Below is the output. This is on a CME 2901 running 15.1(1)T

Any help would be appreciated.

RECONYX-2901#test voice port 0/0/0 thl-sweep verbose
Original impedance 600r. Input signal level=-41dBm

testing 600r...... Input Signal level=-39dBm
Freq (hz), ERL (dB), TX Power (dBm), RX Power (dBm)
354        5         -6              -11
554        6         -6              -12
754        6         -6              -12
954        6         -6              -12
1154       6         -6              -12
1354       6         -6              -12
1554       5         -6              -11
1754       5         -6              -11
1954       5         -6              -11
2154       4         -6              -10
2354       4         -6              -10
2554       4         -6              -10
2754       4         -6              -10
2954       4         -6              -10
3154       4         -6              -10
3354       3         -6              -9
testing complete for 600r. ERL=5

testing 900r...... Input Signal level=-43dBm
Freq (hz), ERL (dB), TX Power (dBm), RX Power (dBm)
354        10        -6              -16
554        9         -6              -15
754        9         -6              -15
954        8         -6              -14
1154       7         -6              -13
1354       6         -6              -12
1554       6         -6              -12
1754       5         -6              -11
1954       4         -6              -10
2154       4         -6              -10
2354       3         -6              -9
2554       3         -6              -9
2754       3         -6              -9

ERL very low. set_impedance to 900r failed !!!.
RECONYX-2901#


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Ryan Schwab Wed, 03/02/2011 - 11:44

Running into exact same issue with the sweep method error.

Users are complaining of audio cutting in and out when both parties talk simultaneously.


Did you ever make any headway on this? My initial suspicion is that it is a cabling issue.

johnnywan Wed, 03/02/2011 - 12:10

No, I could not get the auto THL Tone Sweep to work in this scenario. I ended up using the:

Original Tone Sweep Method

http://www.cisco.com/en/US/tech/tk652/tk701/technologies_tech_note09186a0080477a06.shtml

Look at the original tone sweep method section of the document. Basically you have to test each impedence setting manually, one at a time and record the result averages. Pretty easy but time consuming in comparison to the THL Tone method.

Hope this helps.

Ryan Schwab Wed, 03/02/2011 - 13:05

Hi Johny,

I discovered a bug in the IOS (DSP firmware) I was running which describes the exact problem. This is likely unrelated to to the sweep test failing but just an FYI.

/* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";}

CSCth60636 - PVDM3: clipping and choppy audio during double talk

Christopher Graham Wed, 03/02/2011 - 18:17

When the sweep runs into an impedance where the ERL is too low (typically below 6 or 7 on average), it will fail.  The solution is to run the manual THL tone method as suggested above.

And, no.  The bug stated above is not related to the THL sweep failure.  Separate issue.

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