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?

I think you are correct in that it is probably just an old protector. I have a side view and can see one of the terminals.

I could bypass it by disconnecting that line and running a new line to the kitchen. My current problem is that when I disconnect that line, I'm back to the hum caused by mj on the rest of the house (garage and alarm).

Regardless of whether the 2-line is connected or not, I am getting a hum on the kitchen phone. Connecting the 2-line phone with or without mj makes no difference.

Is it possible that the protector and mj are both causing interference that are canceling each other out on all phones except the kitchen (closet phone to the protector)?

I doubt very much if one trouble would cancel another.

Your two line phone. Does it have a line 1/2 line 1 line 2 or is it line 1/2 line 2? Two jacks vs 3. If it just has two I'm sure one of the jacks will be for two lines ie 1/2. If so make sure your base cord is NOT a 4 wire cord as that could be a source of trouble, same with the cord to the MJ. Just the center pins should have wires.

If you have access to a volt ohm meter you might want to disconnect at the NID and make sure your house wiring is clean also.

The 2-line phone has 2 jacks; 1/2 and 2. I verified that I am using 2 wire base cords for both.

To check using an ohm meter, should I short the disconnected wires and check the resistance at each phone jack? If so, do I need to take the protector into account when I check the kitchen line? What would be the maximum resistance expected?

Just look for any faults. Check tip to ring, tip to ground and ring to ground. Don't worry about the resistance of the loop as you're looking for something that causes a hum.

Another thing is go to the NID and plug in a plain ol' phone and make a call, see if you hear the hum from there.

I'm assuming this is just a low frequency low level steady hum. Correct?

Yes, it is a low frequency low level steady hum.

So its a new day and no rain. Back to original situation, when mj is plugged in thers is hum on verizon line. When mj is not connected, everything works fine. I'm really confused about yesterday and why things kinda flip-flopped and there was always a hum on the kitchen phone. My wife is convinced it has to do with the rain. I don't think so. I did check a few things today.

Plugging a phone directly into the NID provides a good dial tone with 51.8vdc across the Ring and Tip. This NID (and I assume most of them), disconnects the house feed when you plug a phone into the NID.

I disconnected the junction box that connects the alarm to the office and kitchen lines. I verified that I have a good dial tone with 51.8vdc across the Ring and Tip from the alarm. I also measured Ring to ground at -51.4vdc and Tip to ground at 0 (I was on the 200v scale).

The kitchen line R->T was 1mv with the cordless phone connected and 0mv without.

The office line R-T was 2.9mv with the 2-line phone and mj connected, 2.7mv with mj disconnected, and 0mv with the 2-line phone disconnected.

I connected the alarm, kitchen and office back together and have an SLT plugged into mj. Next chance I get, I will buy a new 2-line phone.

Tip should have no voltage. I've never used the DCA setting for shooting trouble so have no idea what your mv readings mean.

Just look for resistance to ground and across the pair, with the feed removed. There should be no resistance and no voltage.

I can see no reason for your MJ to cause a hum on your 1st line if you're only using single pair base cords to your 2 line phone. If the MJ were inducing noise than it should do the same with a SLT plugged into it.

I don't use MJ, but I know several board member do. I do have a NetTalk DUO into a system with no problems. So maybe our MJ users can let us know if they've ever had a hum on their MJ's.

Even if you don't have DSL or you already are filtered, if the MJ really is inducing noise a DSL filter between it and the phone may cure it. Can't hurt to try.

My old boss used to say" go ahead and try it, you might accidently fix it"

So I finally got around to buying another 2-line phone. It is the same exact model as the original phone. I hooked it up and it too has the same hum. So I have ruled out the phone being defective. I will buy a different phone and see how it goes.

I did notice an option the phone has.... "Set Line Mode". The manual only states "Do not change this setting unless instructed to by customer service." The option settings are Type-A, Type-B, Type-C, OFF.

Any thoughts on what Line Mode is and if that is something worth trying?

I'm guessing 1 or more settings are for low voltage. Some PBXs and some SIP to loop start converters only have 24-30 volts on hook. The Panasonic 4-line cordless system has provision, and I believe some of the AT&T multiline sets have the same capability, as well.

I finally figured it out, well sort of.... from an earlier post:
"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. "

This past weekend I disconnected the open line from the Verizon box and the problem went away.

At the time of the open, I did not have Verizon service but was utilizing that line until I reconfigured. I never disconnected the open line and when I switched to Verizon I was getting some sort of signal that must have been causing the problem with mj. Further more, the open line was laying on roof flashing and when it rained it must of grounded the line causing the weather related problem (without mj there was hum and with mj no hum).


Thanks for all of your help and teaching me a thing or 2.

Glad you finally found the problem!

Sam