Troubleshooting ISDN connection problems in a voice over session can be frustrating for voice talent and audio engineers alike. If you have ever connected to another studio via ISDN and failed to frame or ‘sync up’, it is likely that the two codecs were configured differently. Successful voiceover sessions via ISDN are only possible when both codecs are configured with the same parameters. While many ISDN codecs have auto-negotiation features that allow the unit to set bit rate and algorithm settings upon connection, relying on auto-negotiation still might not get you framed because there are some important parameters that an auto-negotiation will not change, such as the “Decoder Independent” setting on Musicam Primas and RoadRunners.
What is Decoder Independent?
The “Decoder Independent” setting is a crucial parameter for Musicam-to-Telos connections. Digital codecs made by Telos are inherently ‘Decoder Independent’, which means that the Encoder and Decoder can be set to different algorithms (MPEG Layer 2, Layer 3, G.722, etc). With Musicam codecs, this parameter can be changed. Therefore when an ISDN connection is initiated between a Musicam box and a Telos box, it is the responsibility of the owner of the Musicam codec to be sure they are configured to ‘talk’ with the Telos. Changing the Decoder Independent status from ‘No’ to ‘Yes’ allows Musicam and Telos codecs to sync up, providing all other parameters are the same.
Using Speed Dials to Configure
Using factory programmed speed dials is the best way to ensure proper configuration when setting up for an ISDN voice over session. Speed Dials on a Musicam codec can not only dial a set of saved ISDN numbers, they can also perform a Quick Configuration. The Quick Configuration speed dials are preprogrammed with dozens of the most commonly used configurations. The Prima and RoadRunner user-manuals contain detailed charts of the the Quick Configuration speed dials and their respective parameters. The Musicam website offers downloadable PDF versions if you no longer have your manual. Here is an example of the preprogrammed Telos Zephyr configuration for the Prima:
To use a Quick Configuration, determine the settings that you need, press the “SDIAL” button, enter the number from the left hand column on the chart, and then press “Enter”. This procedure will configure your codec with the parameters from that specific chart row.
Should a connection problem arise, it is very useful to have a print-out of your codec’s Quick Configuration speed dials handy. Most of the time, simply punching in the typical Telos or Musicam speed dial will enable you to frame with another ISDN codec. However, sometimes there may be other problems besides the configuration. By knowing that your codec is configured correctly, you can proceed with troubleshooting other areas of concern.
Using Musicam Test Lines
Musicam hosts several lines for testing connections. These test lines are available 24/7 and allow users to connect to one of Musicam’s in-house codecs. The Musicam test lines continuously send music back to your codec which is useful for determining whether you can make outgoing calls and if your ISDN lines are functioning as they should.
These are just a few examples of how the user-manual speed dial chart can help you. The preprogrammed speed dials are a great feature that all Musicam codec owners should be familiar with.
Here is a simple speed dial cheat-sheet for the most common Musicam codecs:
Musicam CDQ Prima & Prima LT – Musicam Codec Configuration: Speed Dial 35
Musicam CDQ Prima & Prima LT – Telos Codec Configuration: Speed Dial 37
Musicam RoadRunner – Musicam Codec Configuration: Speed Dial 18
Musicam RoadRunner – Telos Codec Configuration: Speed Dial 19