I have recently converted my garage into a home office and purchased a "Magic Jack" for my business phone service. The service has worked great with no problems at all on a single-line phone.

I purchased a two-line office phone (ATT 992) so I could receive calls on my home POTS line, as well. With both lines connected to the phone at the same time (via individual jacks), there is a severe hum condition (audible on my end only) that is so bad it prevents Caller-ID and New Call notification from working on both lines.

With just one of the lines connected alone, to either of the input jacks, there is no hum and Caller-ID works fine. This is true for both of the phone lines.

I did an exhaustive internet search for filter devices that might solve my problem, and came across the SNIX. I have been in contact with engineers at SNC Manufacturing -- makers of the SNIX -- and they tell me that their Super SNIX product will solve my problem. And that I will need two, one on each line.

I would be willing to give their suggestion a try if these units did not cost nearly $300 a piece! I am hoping someone out there somewhere might have a more economical suggestion for me. I am an EE and have good electronics skills, so I am not averse to cobbling something together from raw components to solve my problem.

Here are the voltage readings I took for the SNC engineers me:

Open CO circuit, tip-to-ring: 52.5VAC
CO ring-to-ground: 4.5VAC
CO tip-to-ground: 5.2VAC

Open VOIP circuit tip-to-ring: 46.0VAC
VOIP ring-to-ground: 2.0VAC
VOIP tip-to-ground: 45.0VAC

I'd appreciate any help anyone can give me. I am back to using two separate phones, and it doesn't really project the image that I know what I am doing! Thanks!

so your saying that two single line phones work fine but the two line phone doesn't ?


I would try a different two line phone , I m partial to Panasonic for applications like this

(what happens when you reverse the line inputs ?
magic jack to two pots to one )

The two-line phone works great, as long as only one of my two lines is connected. This goes for both input jacks.

When both of my lines are connected, regardless of which input they are connected to, I get the hum and loss of Caller-ID, etc.

Unfortunately, I do not have any other two-line scenario in which to test this phone. But since it works great with a single line connected, I am assuming the problem is not in the phone.

sounds like a poor assumption to me

(you know what they say about that word don't you ? )

Most of these phones have a 4wire jack for two lines or you can use two line cords for the two lines. Try two SINGLE line, line cords, two wire not 4 wire. I'm betting your picking up noise from the computer chassis.

Well, I have a couple of ideas worth looking into:

#1: You should be measuring your line voltages using a DC scale. 45-52 VDC across an open line is normal, ring to ground should be about the same and tip to ground should be minimal. In a perfect world, the tip-ground measurement should be as close to zero as possible. On POTS lines, the tip side is grounded at the CO, so any tip-ground voltages measured will be only minor induced AC influence.

#2: The PC that you are using for your Magic Jack must be grounded. I know, I know, most are. Bear in mind that if it's not, then the voltage from the Magic Jack is "floating", as in no reference potential to ground. I'm no computer whiz, but I'd like to think that all power supply outputs in a computer have a reference point to chassis (earth) ground.

A difference in potential to ground between the two "CO lines" that you are using may be the source of your problem. The common internal ringer circuitry in the telephone set relies upon basic, and VERY basic DC isolation since it's fairly common for both CO lines to have the same reference to ground. This is due to the fact that they typically originate within the same central office and ride over roughly the same length of cable. With two lines that don't originate in this manner, that could be the cause for your issue.

If all else fails, try isolating the computer's chassis ground using a 2/3 prong adapter to isolate the chassis ground by not connecting the grounding terminal on a temporary basis. This will at least help isolate the potential AC interference due to the local ground. Since the Magic Jack is powered by the USB port, there's a good chance that may very well be a floating voltage, causing excessive AC influence between the CO and the computer's power supplies not being bonded together.

Bear in mind that the Magic Jack was not intended to be used in any kind of sophisticated environment. The manufacturer's intention wasn't really much more than to connect a stand alone single-line set to it.

Typical two-line phones aren't sophisticated enough by design to take these issues into account.

lets not forget the wall wart and 9volt battery.

consumer grade , two line phones can be flaky

Occam's razor

"All other things being equal, the simplest solution is the best."

the simplest solution in troubleshooting this would be to swap the phone out


see if the same problem exists on two two line phones from separate manufacturer

I agree with trying another telephone. VTech's quality control has been suspect for years.

AT&T/Lucent branded telephones, manufactured by Philips Electronics and earlier, seem more reliable than the current VTech manufactured models.

Try purchasing another 992 and see if it fares any better.

Wow, thanks for all of the input! I have tried several things as a result:

1. One reply said that the tip side of my Verizon line is supposed to be at ground, but it isn't. So I tried jumping it directly to ground. This killed the hum and related problems when using line one of my two-line phone, but it also rendered the Verizon line unusable.

1a. There's a wire coming out of my NID with a bear end that is just hanging in mid-air. Is this supposed to be a ground wire???

2. I put ground lifters on my computer and all the devices connected to it. This only worsened the hum problem. It did lead me to find a loose ground in my breaker panel, though. My outlet grounds were reading 8 ohms to earth (water pipe). I fixed that, but it didn't reduce the hum.

3. The hum does not change when the wall transformer is disconnected (it powers the speakerphone, clock, and backlight).

4. I tried reversing polarity on each line, with no effect.

I agree that trying another phone or hooking this phone to two other lines would be the next logical step in troubleshooting the problem. I guess I am just cheap. I thought there might be something I could connect to the lines to filter the hum or correct the imbalance.

The SNC engineers have assured me their Super SNIX device will do the trick, but it is almost $300. "Cheap" and $300 don't mix.

I find it curious that no one has mentioned a filter on the line. Is anyone out there familiar with the SNIX? It contains a common-mode choke and a harmonic drainage reactor. I can wind a choke if someone could recommend some specs. But I have no idea what a harmonic drainage reactor is. I am sure I could make one if I did. Any ideas?

Thanks again, all!

You can get a single line one from them a lot cheaper than that, but that should be a last resort.

Per your earlier post it only happens when both lines are hooked up, so I'd say AC power induction is not your problem. You've got more trouble shooting to do.

$277 is what their exclusive distributor quoted me for a single-line Super SNIX. And they said I'd need two -- one for each line. I guess if I have to spend some money on this problem, I'd rather try another $50 phone!

Read the post in "general" about chokes..I've bought them. In my opinion that is not your problem. Since we're talking 3rd party here I'll tell you they are about the same price as the phone for end of line chokes. Part number is in the other post.

If this were AC power induction you would have it no matter what. Wouldn't matter if one line or 10 lines were hooked up, you have it on each line. Like I said, you have more trouble shooting to do.

A cheap and easy solution!

After a few days of brainstorming trying to figure out how to completely isolate my telco line from my VOIP line, I thought about trying one of those RF phone jack extenders. The transmitter unit deals with whatever crap the phone company is sending and selectively transmits the voice frequencies to the receiver.

The receiver then emulates a clean phone line that is not referenced to ground anywhere which should not give me any sort of unbalanced, hum-inducing condition. This was my theory, anyway.

Well, $50 and a few minutes later, my problem was solved! I know this is not a "professional" solution, but look at what I am dealing with... a pieced-together kludge of a system! So what's one more kludgie piece??? Hey, it works great, I get to keep the (most likely, crappy) phone that I like, and I am happy. Just thought I would post this for anyone out there with a similar problem.

Thanks again to everyone for your input... it got my brain going and really did help.

Wow. Sure glad that I found this forum. I am having a very similar problem. 2 line AT&T phone (model 992). Separately each line is clean. When I add my VoIP line to the same phone as my POTS line I get hum on the POTS line. This is the second post that mentioned AT&T phone in the problem statement so it could be the root cause. I like the phone isolation solution using a "phone jack extender." Did you put it on the POTS line or the VoIP line. I would guess the VoIP side. I will be going to Radio Shack tomorrow and pick one up.

I went back and read your 1st remark. You went back to using 2 side by side phones. That is the ultimate test for the lines. If ok, it is the phone, or the cord. Some 2 liners use ac for intercom, and have a conference that ties lines together, or has a flat cord and needs a twisted, for noise and xtalk. They shouldn't interfere any more than 2 different phones. Pairs can be split and xsed with dead wires and pick up noise. Inbalance, and sounds like ground humm, but the 2 seperate phones would be noisy too.

Scott, it does not matter which line is isolated, however I would use it for the VoIP line. This way, in the event of a power failure, where you would lose the IP line anyway, you will still have your POTS line working on the phone in case of emergency.

Scott, contrary to the conflicting advice, it DOES matter which line you run through the "extender"... at least it does in my case. For the reason that Ed stated, I first ran the VOIP line through and connected the Verizon line directly to the phone. This resulted in the same bad hum on BOTH lines and non-working Caller-ID on BOTH lines as if the extender was not connected. So the only scenario that worked was to "filter" the Verizon line and direct connect the VOIP line.

Can you tell me what brand of extender that you used. All the one that I see use the AC powerlines to transmit the signals.

Thanks for the input. You are right... there was NO hum when using two separate phones. But the problem was not with the phone cord. And it had nothing to do with the AC power supply hooked to the phone, as the problem still existed with the power supply disconnected.

I suspect it has something to do with the simple internal electronics of the consumer two-line phone like someone had mentioned earlier. It was just not meant to marry the wildly variable conditions of the archaic switched telephone network with the relative precision of even such a simple device as the VOIP unit I have.

I am sure I could have purchased a more expensive phone or a commercial phone system (I am partial to the old Inter-tel Axxess, having maintained and programmed one for 12 years), but since I am just a guy in an office in my home right now, I wanted to get this thing working as quickly and cheaply as possible.

And during a power failure, I won't be working in here anyway because I need my computer for all the work that I do.

My AT&T 992 phone is a few days old. I can return it to Staples for another 2-line phone.

Any recommendations for a good quality 2-line phone that has a 2.5mm headset jack and caller ID?

Unfortunately, there is no good quality two-line telephone set. Any consumer-level telephone (4 lines or less) is manufactured to be disposable. Panasonic is probably the highest level of quality, but their products are expensive and not carried by all retailers. Retailers don't like to carry expensive products. The "at&t" products are about the best that you are going to find in the two-line phone price arena through mainstream retailers.

Remember that the "at&t" name is just a licensed trademark; AT&T hardware has been gone for decades and today's "at&t" has nothing to do with the manufacture of phones. This name has nothing to do with quality; it's a matter of which off-shore manufacturer came up with enough money to buy the use of the retired (AT&T) trademark.

Also, remember that consumer-level products are priced to make it difficult to justify warranty service. They may have impressive long-term or even lifetime warranties, but the shipping/handling charges and restrictions make them cost-prohibitive to the end-user.

If you want the quality of a real phone system, you are going to need to pay for one. The "buzzing" issues that have been discussed throughout this thread are indicative of how these consumer-level products DO NOT perform.

Retailers tend to leave consumers with the misconception that phone installations are a "do it yourself" project, just like painting a bedroom. "If the plug fits, then it must work, right?" These same retailers also encourage people to run their own gas lines, replace water heaters, wire hot tubs and install new electrical services on their homes.

No offense intended, but there really isn't an easy answer to your question otherwise. Buying additional retail gadgets to isolate an inherent problem with the product is like using a Band-Aid to close a gaping wound.

It was just not meant to marry the wildly variable conditions of the archaic switched telephone network with the relative precision of even such a simple device as the VOIP unit I have.


:rofl: I think you have it backwards my friend! I really wish people would see VoIP for what it really is, a can of worms. If the VoIP device were designed properly to telecom standards by someone who actually took into consideration that it might be used with a multi-line phone you wouldn't have this problem.

-Hal

Here is long list of two line wired phones

https://www.hellodirect.com/hellodirect/Shop?sort=price&actn=100300&dsp=30005&PCR=1%3A1%3A5%3A25%3A240%3A2040&numDisp=100

Anyone have experience with RCA or Aastra phones?

Well I think you're trying to take one cheap piece of junk (VoIP) and make it work with another cheap piece of junk.

That being said and making me feel somewhat better, are you plugging your VoIP in the 1st or second line and have you tried it both ways? Reason is the 1st line has the intercom digitally super imposed on it. So possibly that's the problem.

Pay me now, or pay me later.

Its a catch 22 affair.

I have been trying it with the POTS on line 1 and VoIP on line 2. As soon as I plug in VoIP I get a hum on Line 1. No hum on the VoIP line. The VoIP line is a straight single run from the cable modem/ATA to the phone. I have tried multiple cables. The cable does not pass any power lines.

If I switch the lines with VoIP on Line 1 and POTS on line 2 than the hum gets MUCH worse and it becomes much louder and sounds like more than a hum.

I think that I will try a different 2-line phone before trying the RF jack extender. Anyone have experience with the RCA 2-line phone (25202RE3). I can get a new one thru ebay for $70 which includes shipping.

Go to your local best buy and two or three units. Test em and return the ones you dont want.

p.s. Get a panasonic like said earlier might be your best bet.

Scott:

I purchased one of the RCA units at Wal*Mart for my father and it seemed to work well for his application. Their price was about $20.00 less. While I don't advocate using these devices, if it works for you, then that's all that matters. All home centers carry these units as well, so maybe you can save yourself some shipping time by going that route. I am sure that if it doesn't work, you will be able to return it.

I have a Linksys PAP2 VOIP adapter connected to a Panasonic KXT-30810, along with a Verizon landline. The setup works fine, has been for 3 years.

I expect your setup would work fine if you were using a Linksys PAP2. The problem is that your Magic Jack isn't isolated from ground, and is causing a ground loop.

Using the phone extender breaks the ground loop, solving the problem.

Another option would have been to plug the computer into an isolation transformer. These occasionally turn up on Ebay pretty cheap, intended to provide ground isolation to computers used for medical purposes.

Brian - I am using a Moto cable modem with an integrated ATA. If isolating the cable modem with a transformer would solve the problem then I would consider it.

The phone extender is interesting, but I would want to use it on the VoIP line which did not work for kjkauffman.

Planning to swing by Walmart or Bestbuy and buy and few 2-line phones.

"If isolating the cable modem with a transformer would solve the problem then I would consider it."

Does the cable modem have a 3-prong plug? Most do not. I don't recall seeing one with a 3-prong plug in a long time.

However, it can still be grounded through the cable TV line and there are ground isolators that can be used to solve the problem... The Viewsonics VSIS-EU is one such device. I read a report that a user on Cox cable got this supplied for free from Cox due to a ground loop problem involving a plasma TV.

There another place that it could be causing a ground loop--the Ethernet cable. Some cable modems were or are supplied with a screened twisted pair network cable. This has a metal shield around the RJ45 connector. If you are using a cable like this deposit it in the nearest trash can and replace it with a normal one.

Finally, if you are using the USB port on the cable modem I suggest switching to the Ethernet port. The USB port is a definite source of a ground loop.

Twisted pair Ethernet is, unless it's that screened twisted pair variety, isolated and will not cause a ground loop.

As a test I will try taking off the CATV and Ethernet cables. I can also unplug the cable modem from the AC because it has a battery back-up. These tests could provide some interesting data. Thanks for the suggestions.

I also just ordered three different 2-line phones from Circuit City - RCA, Panasonic and IntelliTech. CC offers free shipping so I can try them all and drive them back to the store for a refund.

With both the AC and CATV cables pulled off of my cable modem the hum goes away. The modem was running off of batteries. If I just reattach the CATV cable the hum comes back. Same is true if I just connect the AC and leave the CATV off.

Not sure where this leaves me. I will have 3 more phones delivered from Circuit City in about a week.

I like all the Aastra phones I've come across..

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

I would check to make sure the cable tv is properly grounded outside.

If pulling off the CATV cable and leaving on the AC cable results in hum then I am not sure how adding just a CATV filter is going to help me. One costs $11 and the other is $50 which seems a bit steep.

Keep those suggestions coming. I really hope one of the three phones that I just ordered will solve this problem.

Still wondering why the RF jackextenders dont work on the VoIP line. For me the VoIP line seems to be the source of the hum on my 2 line phone. I would consider isolating it if none of the new phones work.

If you decide to buy a CATV isolator use the Viewsonics one, it is designed to work with 2-way services. (As a very temporary test you could connect two 75-ohm to 300-ohm matching transformers back to back; I don't know that this will work properly and allow your cable modem to sync, plus it will result in signal leakage; however as a temporary test it may be OK. The matching transformers should act as an isolator. But they're not shielded at all so....).

That in conjunction with an isolation transformer should solve the hum problem you are having.

Do you have a link to the Viewsonic isolator?

For $10 I bought the one from Dayton. Hopefully it wont interfere with my internet or voice service.

The Jensen transfer was $50 which was too steep a price for this test.

EDIT - Found it here:
https://www.broadbandamps.com/Products/GroundIsolator.htm

I am looking at one of these too
https://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120244590618&_trksid=p3907.m32&_trkparms=tab%3DBidding
If I can get one for under $30 than I would give it a try too.

Between three different 2-line phones, a filter on the CATV cable and isolating the AC I better be able to hear a pin drop!!!

https://cgi.ebay.com/Medical-Grade-...543QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

also, another cable TV ground loop isolator is the TII 220):

https://cgi.ebay.com/TII-CABLE-TV-C...803QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[/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.