atcomsystems.ca/forum Forums TDM Business Telephone Systems Comdial Telephones & Systems DSU II humming sound on some phone lines

no sounds like you have bad line ports need to switch line ports and or replace if you don't have enough good ones. you say the noise is there when disconnected from the dsu, how do you know.

It's not the ports the humming noise follows the line no matter what port on the DSU I plug it into. I know the noise is there if I disconnect the phone line from the DSU because I plugged that phone line into a regular phone, but as I noted in a previous post the noise is much less noticeable when the phone line is hooked to a regular phone.

Check your loop current.

The loop current is 49ma and the AC voltage is 4.4 VAC from tip to ground and ring to ground. That should be enough volts to be causing AC induction noise, but all 4 lines have about these same numbers and only two lines have the noise. At this point since the phone company (Frontier) won't fix it, I think I'll switch to VoIP does anyone have experience with www.nextiva.com?