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Pulsing static on an E1 (UC560)

Noticed an issue with a customers UC560 where when there is silence on the line (eg both parties don't speak) where you get this pulsing static (best way I can describe it).  Phones in use are 525G units running 7.4.6.  UC560 is running the 8.0.4 support pack.  Interface with the PSTN network is via a 20 Channel E1.

Anyone had anything similar?  I've quizzed internally at work and the one suggestion i've had is to upgrade the phone firmware.  The engineer had seen a similar issue on a 79XX series phone and an upgrade fixed the issue.

Thanks in advance

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Hall of Fame Master

Re: Pulsing static on an E1 (UC560)

Send "show network-clocks".

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Re: Pulsing static on an E1 (UC560)

  Network Clock Configuration
  ---------------------------
  Priority      Clock Source    Clock State     Clock Type

     1          E1 0/2/0        GOOD            E1
     7          Backplane       GOOD            PLL

  Current Primary Clock Source
  ---------------------------
  Priority      Clock Source    Clock State     Clock Type

     1          E1 0/2/0        GOOD            E1

There is also no clock slips shown in the sh controller E1.

Thanks

Nathan

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Re: Pulsing static on an E1 (UC560)

Wondering if after the E1, how does the call route and is it VoIP at any leg.

Then i was thinking VAD or silence suppression.

Then I found this...

http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a00800a9982.shtml

Steve

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Re: Pulsing static on an E1 (UC560)

Ended up trying out firmware version 7-4-7 which is the latest avail for the 525G.  This appears to have fixed the issue.  I'm upgrading the clients phones tonight to bring them up to the new version of code and going to see how things are on Monday.  I've been to site today and the test phones I upgraded appeared to have the issue resolved on the new version of code.

Cheers