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Blog Central

Troubleshooting Zephyr Codec Connection Lock Issues

Posted by Clark Novak on Aug 31, 2011 1:56:00 PM

From the Tech Tip grab bag: "My Zephyr appears to connect to the Zephyr at the other end, but the codec doesn't lock.  Whats happening? How do I fix this?"

Telos Support Swami Ted Alexander explains "You can start by checking both Zephyrs in ISDN loopback mode. If you can lock to yourself in loopback mode, the great likelyhood is that the difficulty is external to the Zephyr, and probably in the ISDN lines. Some customers have been experiencing inability to lock at 64 kHz bitrates, but are able to lock at 56 kHz. Within the past year or two, some telephone providers have discontinued support for 64 kHz service, so try 56 kHz instead and see if you achieve lock. You can also try connecting, and then selecting the G.722 codec. G.722 is a lower speed codec and occasionally locks when the higher speed codecs will not.

"There could also be a problem with the long distance carrier handling data calls. Remember, all Zephyr codec calls are data mode calls and the ISDN provider needs to provision the ISDN lines for data transmission. So, if you can lock the Zephyr to itself in loopback mode, but not over the ISDN connection, then the next call should be to the ISDN local carrier and/or long distance carrier. The instructions for ordering the proper provisioning of ISDN lines for Zephyrs can be found toward the back of the user manual."

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Topics: IP Audio Codecs & Transceivers