I changed from a tdm100B card over to an Adtran 750 as I added more PSTN lines last week. I have a Sangoma A104u card and 12 channels FXO connected to PSTN lines. I am experiencing very poor audio quality with hum on the lines and poor volume. When I connected the Adtrans I upgraded the firmware to the latest and reset the config to the factory default. I also upgraded Asterisk to 1.2. I am at a loss to explain why the quality has become so poor, has anyone any advice? -- Chris Mason
> I changed from a tdm100B card over to an Adtran 750 as I added more PSTN > lines last week. I have a Sangoma A104u card and 12 channels FXO > connected to PSTN lines. I am experiencing very poor audio quality with > hum on the lines and poor volume. When I connected the Adtrans I > upgraded the firmware to the latest and reset the config to the factory > default. I also upgraded Asterisk to 1.2. > I am at a loss to explain why the quality has become so poor, has anyone > any advice?I'm not useing a 750, but just suggesting a possibility... Check to ensure the fxo lines have proper termination/impenance settings. 600 ohm in the US, etc. There was someone trying to use another channel bank some time ago in the Colorado area (I forgot the exact make/model), and the fxo card specs were actually listed as 15,000 ohms (no 600/900 ohm at all). He had the same 'hum' issue, and that was certainly understandable.
How would you test the audio properties of an FXO line? I am interested in a way to generate a tone of 1 khz, send it out a line, measure hwo the channel bank has converted that tone to real audio, and measure the attenuation. Otherwise it all seems like guesswork. I do have a Dynatel 745 Subscriber Loop Tester, although I have no idea how to use it. -- Chris Mason NetConcepts (264) 497-5670 Fax: (264) 497-8463 Int: (305) 704-7249 Fax: (815)301-9759 Cell: 264-235-5670 Yahoo IM: netconcepts_anguilla@yahoo.com