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Echo on IP to IP phones (7940's) and out to gateways

Ive got a problem on a site with echo. The customer is telling me that they are getting echo on internal (IP to IP) and external calls (external destinations to the PSTN and to calls via a gateway to a Philips system). Has anyone come across this before and is there a fix?

CCM is ver 3.3.3

Phoneloads are P00305000400

Gateways are flash:c2600-is-mz.122-15.T14.bin

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Re: Echo on IP to IP phones (7940's) and out to gateways

Rule of thumb when dealing with echo:-

Echo on one end is typically generated at other end

Echo is not introduced on digital links

Introduced by 2 to 4 wire conversion in hybrid and impedance mismatch

-8dB to -16dB drop end to end (-12dB being nominal)

Know loss plan of the PBX (AGC, Padding)

# or * DTMF tones approximate 1004Hz @ 0dB tones

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