atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Telecom Service & Providers MagicJack causing hum on verizon pots line

Initially I had pots phone service through RCN. I added MagicJack as a second phone line and purchased a Radio Shack 2 line phone (43-338).
Everything worked fine.

RCN then converted me from pots to voip. The 2 lines still worked fine but due to network problems with RCN's internet service, we had sub-par phone service and decided to switch to verizon.

Once the switch over to verizon occurred, I noticed a hum in the verizon line. Although, the 2 line phone has the worst hum, the other phones also experience the hum. I thought the 2 line phone hum might have been louder since it does have a volume amplifier.

After a lot of troubleshooting, I determined that it is coming from the MJ line. I disconnected MJ from the pc and plugged it into a laptop (located next to the pc) using the existing phone line. The hum disappeared. So somehow I am getting some hum/feedback from inside the pc.

Even with the pc off, I still get the hum. If I unplug everything from the pc, no hum. I connected the power supply and the hum returns. I verified that the pc is properly grounded. I also noticed that if the pc is unplugged but I attach other devices (i.e. LAN cable, HDMI to TV, etc), the hum returns.

So I am stumped. Any advice other than "don't use the pc, use the laptop" would be greatly appreciated.

Try using an extension cord between the MJ and the PC USB port so that you can move the MJ away. Also try changing the physical orientation of the MJ versus the PC.

As I sit here thinking about this, I wonder if your outlet is TRULY wired correctly and do you have some sort of ac protection that is creating a resistance in the ground circuit?

Here is what I have tried to no avail....
I verified the outlet is grounded using a outlet circuit tester. Also, the UPS will indicate if the outlet is not properly wired.
I connected the pc directly to the outlet, with and without an additional grounding cable.
I connected the pc through the UPS.
I connected the pc to another outlet.
I used a USB extension to extended the mj 6 feet from the pc and used a different phone line. The path is now not located near any other devices or power sources.
I connected mj to a different pc in the opposite corner of the room. I'm not positive but I believe this outlet is on a different AC phase and/or breaker. Doing this test makes me wonder about trying the laptop again, running off of AC instead of battery.

Using the laptop with AC did cause the hum to return. Unplugging it and running on battery make the hum disappear.

Now I am totally clueless with the hum and even more so, why it never existed with RCN voip or pots service.

You stated the other phones have the hum also, but the two line phone is worse. Unplug the two line phone and see if the other phones still have the hum. I suspect the two line phone.

How about if you plug a SLT into the MJ hum or no hum?

If I unplug the 2 line phone, the hum goes away. The problem only exists when the 2 line phone is connected using mj and pots. If I disconnect mj, the rest of the phones are fine. I would have suspected the phone except for the fact that the phone work fine for a year and as soon as I switched to verizon the problem began.

I guess I could try a different phone but I really like this one and it wasn't cheap.

justbill, what is a SLT?

SLT=Straight Line Telephone plane ol' phone.

Move your two line phone away from any electrical interference if plugging an SLT into the MJ is clear and no hum. Get it at least a few feet from your computer and monitor, or printer and whatever else you may have close to the phone. I still think it's the phone either picking up some AC induction or going bad, probably the first.

IF your two-line phone has a conference feature, make sure the CONF button isn't partially depressed and that your two lines aren't conferenced together.

Any chance your new Verizon line has DSL service on it?. The "data hum" could be inducted across the pairs of line 1 and line 2, you would need a DSL filter on both if that is the case.

Thanks for the feedback but none of those things apply and/or helped. Here comes a new twist......

Today (rainy) the verizon phone line has the hum. I checked the mj line and it was disconnected. I connected it and the hum went away. I disconnected the 2-line phone completely and check the garage phone which is an SLT. It had a hum. The same thing with the kitchen phone. It got me thinking....

A few years ago all of the house (kitchen and office) phones were dead. The 50 year old main line from the box must of had an open. The phone line at the alarm was fine and so was the return line that went to the garage and the rest of the house. I disconnected the house end and ran a line from the alarm, down into the basement to junction box where the kitchen and office lines connect. Everything was fine.

Although I cannot physically access it,I can see where the original phone line came into the house. I looks like it is connected to a black box (transformer?) where is then feeds the kitchen and office. I cannot see all of the wiring, I am just guessing. This is about 15 feet from the junction box that I tied the alarm into.

So I did another test... I disconnect the line to the kitchen phone / black box. Now I'm back to original situation where the verizon line has a hum when the 2-line phone is connected to verizon and mj. I reconnected everything and there is no hum with the mj connect but a hum without. A much better situation but I did notice a slight hum from the kitchen phone.

It really makes me think that the hum is somehow related to mj and the black box. Any thoughts?

Once again, your help is greatly appreciated.

That's probably just an old protector. I would guess the far left one pictured here.

Remove the carbons as they could be activated, it's just being used as a connection point anyway.

EDIT: Well forget that you said you can't access it. Can you by-pass it?