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Why does my fax machine disrupt my VOIP service? Whenever it's plugged in, I lose service. Why?

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VoIP service being disrupted when you plug in your Fax/Printer/All-in-one device?


While I was a Technician working for Comcast, I only ran into this problem one time during my entire cable career as a Comcast CDV (Comcast Digital Voice) VoIP telephone installer. The problem is very rare but if it does happen, you will be pulling your hair out trying to figure out how to fix it. This type of problem only effect VoIP service to my knowledge.

What happens is every time you plug your fax machine, or a 'all in one' printer/fax unit into one of your phone jacks or a splitter, you lose all dial tone. Soon as the device is un-plugged, service restores back to normal.

Good News:
The good news is you don't have to buy a new fax/printer device to correct the issue.

Bad News:
The bad news is you will need access to a pair of wire cutters, a uncompressed or virgin phone fitting, and telephone fitting crimpers. If you can't access these type of tools, you can get a pair of cheap crimpers for about $10 and a small bag of telephone fittings for about $5 at the Home Depot or a store similar. No need to buy top of the line tools because you will only need to use the crimpers once to fix this issue. In fact, you could even return the crimpers when your done if you'd like.

How to fix this problem:
I'm not 100% why this happens but I do know how to fix it easily. A standard fax and telephone device only uses (2) out of (4) wires on a phone cord. In your telephone cord which is commonly known as silver satin for it's silver color and smooth texture, you will notice there are a total of (4) tiny wires inside. These (4) wires fit into your telephone fitting with much ease. To stop this problem, we only want two of the wires to go into the fitting and not all (4). Commonly, you would just insert all (4) wires, crimp the fitting and it's ready for use.

First, your going to want to take the telephone cord that came with your fax machine and cut the current phone fitting off on one side only. It doesn't matter which side is cut as long as one of them is. Next, your gonna take your phone crimpers and strip the cord accordingly to put a new fitting on the side you severed. Now you are going to do something that is not normally done.

First I will give a brief explanation of what the (4) tiny wires mean, and do. The inner pair (middle two) wires are the primary pair. Their colors are usually 'Red and Green' and in some instances 'Solid Blue and Blue/Blue-White'. Then you have the outer pair. These wires are typically 'Black and Yellow' while sometimes also being 'Solid Orange and Orange/Orange-White. These 4 little wires which contain (2) unique pairs which are capable of each having their own phone numbers. In most cases, the outer pair is never used. It is still crimped into the fitting because it's less work in strip and insert all 4 wires, rather then cut off the outer pair and then insert the two inner wires into the fitting.

We have to do exactly just that to fix the problem. We must go above and beyond and simply remove the extra outer pair of wiring and prevent it from being crimped into the fitting. I have painted a simple diagram below that out lines what should be done before making the phone fitting crimp.

Click Thumbnail for better view below


Please excuse my artwork, it's just a basic diagram to show the end result before making the crimp on your new fitting. Normally, these kind of telephone cord modifications are not needed. If your wondering if you can buy a modified one in the store the answer is no. Not to my knowledge will a place like Radio Shack sell a 6FT Silver Satin cable with only one pair.

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