3 Replies Latest reply on Sep 4, 2012 9:56 PM by sunstatetech

    Echo and low volume on FXO

    sunstatetech New Member

      I am working with a NetVanta 7100 right now. They recently switched from a PRI to analog lines. There are a total of 6 analog lines, two in the built-in FXO ports and four on a quad FXO module. They are experiencing echo and low volume. Here are the specs on the unit:


      Model:  1200796L1

      Fimware:  A2.07.00.SB.E

      DSP software version: G1.A2.06.19

      DSP hardware version: Freescale MSC7116


      So as you can see, this is the older model (L1 as opposed to the E1) with the older DSP. Also, A2.07 is the newest firmware that is supported on that model. The FXO ports are all set to default:


      Impedance:  600 Ohm+2.16uF

      TX gain:  0.0

      RX gain:  0.0


      Following the NetVanta 7000 Series Analog Troubleshooting Guide, first thing to do is run the Echo Return Loss (ERL) tool, which should automatically set the correct impedance for you. However, the ERL is not supported on units with the older DSP. Does that mean that the older DSP's don't have any echo cancellation at all?


      The troubleshooting guide goes on to talk about echo and low volume in more detail. It says to help eliminate echo make sure the impedance is set correctly and lower the RX gain. Well, I have two problems with that; I have no idea what to set the impedance to and they are already complaining about low outbound audio volume, so lowering the RX gain would just make that worse.


      I really need some help here on what troubleshooting steps I should take to help eliminate these problems.