Hey guys, I am trying to diagnose a hum in my FXO lines I am using an Adtran 750 with 8 FXO ports. I am getting a pretty bad hum on the line during a call. I have checked the Telco side of the 66 block and there is no hum there so it's my problem to fix. I have tried to lower the gain but that reduces the call volume to much. Where else should I be looking? Setup as follows Dell PE1950 server Redfone Quad port fonebridge2 Asterisk 1.2.18 Zaptel 1.2.18 From redfone Adtran 750 Channel Bank with 8 FXO and 16 FXS Two PRI connections to fonebridge TIA Mark -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.digium.com/pipermail/asterisk-users/attachments/20071006/c4da1872/attachment.htm
Maybe approach this problem at the wall socket? Could there be ground issues in the building that the telco has filters for but asterisk's box doesn't? A line conditioning UPS might help. Moj Mark Bell wrote:> > Hey guys, > > I am trying to diagnose a hum in my FXO lines > > I am using an Adtran 750 with 8 FXO ports. I am getting a pretty bad > hum on the line during a call. > > I have checked the Telco side of the 66 block and there is no hum > there so it?s my problem to fix. > > I have tried to lower the gain but that reduces the call volume to much. > > Where else should I be looking? > > Setup as follows > > Dell PE1950 server > > Redfone Quad port fonebridge2 > > Asterisk 1.2.18 > > Zaptel 1.2.18 From redfone > > Adtran 750 Channel Bank with 8 FXO and 16 FXS > > Two PRI connections to fonebridge > > TIA > > Mark > > ------------------------------------------------------------------------ > > _______________________________________________ > --Bandwidth and Colocation Provided by http://www.api-digital.com-- > > asterisk-users mailing list > To UNSUBSCRIBE or update options visit: > http://lists.digium.com/mailman/listinfo/asterisk-users
If necessary a 1:1 transformer on the voice lines might clean your audio up for you. One transformer on each line. On 10/6/07, Mark Bell <markb at pilgrim.com> wrote:> > Hey guys, > > > > I am trying to diagnose a hum in my FXO lines > > I am using an Adtran 750 with 8 FXO ports. I am getting a pretty bad hum > on the line during a call. > > I have checked the Telco side of the 66 block and there is no hum there so > it's my problem to fix. > > I have tried to lower the gain but that reduces the call volume to much. > > Where else should I be looking? > > > > Setup as follows > > Dell PE1950 server > > Redfone Quad port fonebridge2 > > Asterisk 1.2.18 > > Zaptel 1.2.18 From redfone > > Adtran 750 Channel Bank with 8 FXO and 16 FXS > > Two PRI connections to fonebridge > > > > > > > > TIA > > Mark > > > > > > > > _______________________________________________ > --Bandwidth and Colocation Provided by http://www.api-digital.com-- > > asterisk-users mailing list > To UNSUBSCRIBE or update options visit: > http://lists.digium.com/mailman/listinfo/asterisk-users >-------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.digium.com/pipermail/asterisk-users/attachments/20071008/daaeedbd/attachment.htm
Mark Bell wrote:> > Hey guys, > > I am trying to diagnose a hum in my FXO lines > > I am using an Adtran 750 with 8 FXO ports. I am getting a pretty bad > hum on the line during a call. > > I have checked the Telco side of the 66 block and there is no hum > there so it?s my problem to fix. >Is there hum on the line ONLY when the FXO port has closed the loop? At the demarc? When the buttset closes the loop? Or is the hum introduced on the Asterisk end? All of the FXS ports clean and clear? Are you sure it is 60 Hz and not 120 Hz? Longitudinal imbalance introduced by a defect in one port on the FXO card? All 8 ports on 2 cards? Remember that standard analog Central Office lines ( loop start ) are very much like a balanced audio line with DC superimposed for supervision. The DC is introduced at the CO end with one side grounded at the CO and the other at ( open circuit ) -48VDC, and a ground on the subscriber end will introduce hum, or if low enough resistance will keep the line in an off hook condition. Swap the Adtran cards if only on some circuits, and make sure the 750 is well grounded. John Novack -- Dog is my co-pilot