atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Telecom Service & Providers Strange hum problem has me at my wit's end... please help!

[/QUOTE]Sounds like Brian might be on to something. Perhaps one of these would be worth trying:
https://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=180-075%20

https://www.cs1.net/cables/products/jensen_transformers/VRD-1FF.htm [/QB][/QUOTE]

According to Part Express the VIT-1 isolation transformer will not work with Cable modems. It blocks the signals from the cable modem back to the head end.

Here is a good price on the Viewsonic isolator -
$6.64 including shipping. Claims to work with cable modems too.

https://cgi.ebay.com/VIEWSONICS-VSI...803QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

EDIT; Looks like the final prices when the auctions are over is closer to $20.

Viewsonics (actually Emerson Network Power now) is a supplier to cable companies, that to me indicates that it will do what it's supposed to without causing problems. Same is true for TII, you may have seen their name on telephone circuit protectors. No cable company wants to install something that going to result in truck rolls that cost an average of $75 each.

After quite a bit of testing I have concluded that the AT&T handset was the basic problem. I have evaluated 4 different telephone vendors. AT&T and ITT both had a hum when connecting a VoIP circuit to the second line. With Panasonic and RCA there was no hum. I selected the RCA handset because of its design. It has separate volume for the speakerphone, handset and headset which I like.

Just for good measure I add a Viewsonic filter to the CATV line going into the cable modem. It made no improvement on the AT&T phone. I also have 2 chokes coming which will go the phone lines. I lost an auction for an AC isolation transformer which it turns out is not needed.

As you can see I am very finicky when it comes to the sound quality of my phone. Thanks for all the support to put this problem to bed.

I am having the same type of problem, but can't find a solution...

Line 1: Verizon Fios POTS
Line 2: Vonage VoIP


I have a Panasonic 2 line phone that handled them both with no problem for a month or so. Today, the POTS line started giving me a horrible humming noise. The 2 line phone is the only phone in the house. There is a fax machine on line 1 and a postage meter on line 1 - unplugging them makes no difference.

Here's what I've tried:
Disconnect VoIP completely - POTS still hums
Disconnect all equipment - POTS still hums
Connect regular phone right to port on Fios box - no hum
Connect VoIP to either line (without POTS) - each line is fine
Connect POTS to either line (without VoIP) - each line hums
Reverse tip&ring on either - no change

I can't seem to understand why it would work for a month and then have a problem now.

There is another POTS line in the house. If I connect both POTS lines, but no VoIP, there is no hum. HELP!

You'll have better luck opening a new topic rather than adding to one over a year old. Just click on the "Post new topic" at the top of the page.

A new topic has been started going to lock this one so no one gets confused.