Thanks for the tips John. I also forgot to mention the Adtran is a DC unit. The hum is introduced at the asterisk end. If I pull the bridge clips and test the telco side of 66 block the line is fine. I will swap some cards around and see what happens
> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:asterisk-users- > [EMAIL PROTECTED] On Behalf Of John Novack > Sent: Monday, October 08, 2007 2:59 PM > To: Asterisk Users Mailing List - Non-Commercial Discussion > Subject: Re: [asterisk-users] Help 60Hz Hum? > > > > 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 > > > _______________________________________________ > --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 _______________________________________________ --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
