Communications: Voice, Radio and Data - New Phone Lines

I was planning on redoing the phones line in our house, since right now they're cheapy daisy chained together.

I was taking off the insulation between the joists following the old lines to the demarcation area, and to my surprise, I found these gems.

<img src="http://img8.imageshack.us/img8/3659/imagexjh.jpg" height=430 width=640>
Click here to see full-size pic. (http://img8.imageshack.us/img8/3659/imagexjh.jpg)


Apparently they're some kind of ground fault interrupters. The red things I am assuming are some type of fuse. There is 50v going to and from the left one, second is dead (our house is a townhouse, and used to have two separate apartments, probably the line to the 2nd story.)

The secondary pair is grounded onto the interrupters ground. I was thinking of doing something similar to this since I got 1,000 feet of cat3 4 pair on sale for 35usd, only need 1 pair, thinking of grounding the rest to help eliminate RFI.

The interrupter is grounded to the main electrical ground, which is connected to our water pipe. The main issue I have with this, is that I don't want the current to travel back up this line. I'm pretty sure a diode wont be able to stop the current of a lightning strike.

I have plenty of rebar laying around so was thinking about installing a secondary grounding conductor outside. Then ground the phone system to this. Since there would be only the indoor phone lines on this ground, I think it would be less likely to get struck by lightning.

Anyone ever tred something like this?

Anyone know if this would violate any NEC rules?

Those devices appear to be the property of the phone company. I wouldn't mess with them at all. Your responsibility starts on the house-wiring side.

The DC voltage you're reading is the "battery" provided by the telco. AC sound voltage rides on that DC, and the lines also carry AC ring voltage in the neighborhood of 90 volts. Do not add diodes to the house wiring, and do not ground either of the wires!

There should be no RFI in a properly-connected phone system. The twists in the pairs use a method called "common mode rejection" to keep unwanted noises out of the telephone audio.

If you want to redo your system, run a twisted pair of wires from the NID to a punch down block or structured wiring solution, then run individual Cat 3 to each jack location. 4-pair is the most common Cat 3 to use. Some are using Cat 5, but that's overkill if all it's carrying is telephone.

like rick said and don't run your own ground everything in the bldg should be grounded to a common bldg ground

its properly grounded now so don't mess with it

I looked them up, the black one is a 1960s Western Electric model 106A Lightning Arrestor, the white one is a 1970?s Western Electric model 98A Lightning Arrestor.

They are on my side, it goes NID > arrestors > phone.

Western Electric hasn't existed since 1984, I doubt the phone company owns them, or if they do, knows they own them.

I'm not going to mess with the NID's, or the arrestor's ground. I wanted to ground out all the pairs in the cat3 that I will not use. The diode so current (from lightning) does not travel back to the punchdown block via the grounded pairs. But the question is, is there a diode strong enough to handle the current of a lightning strike, or a different way to assure current does not flow back.

I just don't want to ground it to the main ground, have an electrical wire get struck by lightning, then the current traveling to my block. With a secondary rod, less wires, less risk, and I still get a ground.

Can never be TOO careful of RFI in my book. I have a DSL line on my phone line, so less interference is better.

What I'm planning on doing, is using the second black arrestor to make sure current does not travel back on my ground, well at least not enough to do any damage. Basically I am grounding my ground. This may just be paranoia on my part, but if it is connected, the possibility is there. Who is to say that all the current will go to the earth.

Far as I know this isn't against any NEC regulations. The only thing is NEC requires less than 14 AWG wire for grounding wire, but I use 22 AWG to ground components in computers all the time. In old pata cables, every other wires is a ground wire, by default. So hard to say where this rule applies.

I wouldnt ground those unused pairs to anything, just let them float. As was posted, the twist of a pair does the foreign signal rejection. A 'cable' of telco plant will have an outer shield that is bonded to the MGN system, but thats not what we're dealing with here. If you ground just one end of your spare pairs, you may be setting up a mini lightning rod system in the house.. lots of unterminated (on the far end) ground points.

Dont set up a second ground rod. In the event of a neutral line failure in the ac feed, and if your home-made ground path provides a better path to ground than your old house ground rod/wire, then you will get alot of current flowing down your new connection. Will this start a fire ? Your ins co might not be happy. Also, a nearby lightning strike will cause a surge through the earth.. potentially making a different voltage in the area of the 2 ground points. This difference will cause a loop flow between the 2 points.

So you say there is a new(ish) telco demark 'NID' on the outside of the house ? If the new surge/ground protection is inside this NID, I hope they didnt use that yellow/black 24ga wires to make a ground point by just connecting it to the old block protection. There should be some wire at least 14g (preferably 6ga) from the new nid to your mgn connection.

This whole nid program is a mess. Contractors, I guess..

It should be a nid on the outside, with protection, grounded to the house mgn with appropriate sized ground wire. The phone pairs should then enter the house with new wires to some type of punch down block where the homeowner can connect his lines.

AFAIK, once the telco NIDs a place, then all of the inside wire and old protectors etc inside then belong to the customer. It might be different depending on the rules where you live though.

You might want to clean up your carbon blocks in the old protectors, btw. Unscrew the round thing, and pull out the white U shaped block and the small black rectangle on each side. Clean any black dots ('pitting') on both of the carbon faces with emery sandpaper etc (gently, dont remove carbon faces, this is a 'gap' system), slide em back in. If your phone rings while you are handling the connection you will get a shock (90v ac), so I suggest insulated needlenose pliers (or jumper/short the telco side binding posts with something to kill the line).

... is there a diode strong enough to handle the current of a lightning strike, or a different way to assure current does not flow back.
Nothing will stop a direct hit. The lightning arresters that are already there are as good as anything.

Can never be TOO careful of RFI in my book. I have a DSL line on my phone line, so less interference is better. ... I use 22 AWG to ground components in computers all the time.
Computers operate at much higher frequencies where grounding unused wires can be beneficial. DSL operates in the kHz range, topping off at around 1 MHz. As long as you use the proper UTP wiring you'll be fine.

I agree with DaveC72 completely. Do NOT install another grounding system and do NOT "ground out" the unused cable pairs.

As long as you have a properly installed and grounded NID outside I would suggest that you remove the two inside protectors. You would then use a "66" or "110" block to terminate all the station (inside jacks) cables and also the incoming cable and use cross connects to distribute the incoming to the various station jacks.

If you ground just one end of your spare pairs, you may be setting up a mini lightning rod system in the house.. lots of unterminated (on the far end) ground points.

Same goes for the AC, they have unterminated grounds at every receptacle. Also antenna wire is the same way; a pair, and a ground.


Dont set up a second ground rod. In the event of a neutral line failure in the ac feed, and if your home-made ground path provides a better path to ground than your old house ground rod/wire, then you will get alot of current flowing down your new connection.

This is the whole point of making a secondary earth ground, so it is not connected to the AC power ground.


Will this start a fire ? Your ins co might not be happy.

This is the reason for the question about NEC regulations. If I remember right they require less than 14AWG for ground, yet CAT5 cable has TWO pairs of grounded wires in 100base TX/FX mode.

Whats the difference between lightning striking a CAT5 cable, vaporizing it, running to the to the AC ground, and lightning striking the CAT3 cable, vaporizing it, and running to its ground.


It should be a nid on the outside, with protection, grounded to the house mgn with appropriate sized ground wire. The phone pairs should then enter the house with new wires to some type of punch down block where the homeowner can connect his lines.


The way it is now NID > arrestor > daisy chain > phones. The phone lines have the secondary pair grounded on the arrestors ground. (probably since the 1960s.)

Nothing will stop a direct hit. The lightning arresters that are already there are as good as anything.

Computers operate at much higher frequencies where grounding unused wires can be beneficial. DSL operates in the kHz range, topping off at around 1 MHz. As long as you use the proper UTP wiring you'll be fine.
Humm, that is true. I need to find a way to test out cat3 throughput with grounded and ungrounded pairs while under extreme RFI.


As long as you have a properly installed and grounded NID outside I would suggest that you remove the two inside protectors. You would then use a "66" or "110" block to terminate all the station (inside jacks) cables and also the incoming cable and use cross connects to distribute the incoming to the various station jacks.

What I did was use a 66 block and ran a wire down the right side of the left terminators, and another wire down the left side of the right terminators. Then I'll just use the left side as tip and right side as ring.

Just waiting on the cat3 right now to finish it up.



Anywho, I decided not to ground the extra pairs, but I have an even greater modification for a different project. I have these old walls that have the diagonal boards with plaster over it. They have cracks everywhere, so I was going to redo the plaster on them. There is this plastic mesh stuff you use so the plaster has something to grip onto, but instead of the plastic mesh, I'll use metal mesh. Then ground it out and make it into a faraday cage.

How sweet would that be? Only problem is doors and windows. The windows I'm thinking of just using metal screens, and wiring to the mesh. The doors are a bigger problem. My idea for that is to peel the venear sheets off of one side (hollow core doors), glue mesh to the inside, then put back together. Ground it though the hinges.

No one would be the wiser.

Do you live next to a radio tower or something? I just wonder why you're so concerned about RF?

Keep in mind that the frequency at which a Faraday cage operates is dependent upon the size of the mesh. Chicken wire may not block the highest freqs. The only sure way to beat all RF is to line your room with lead foil and ground that. (Don't laugh -- that's one way that audio recording studios eliminate RF.)

You can remove the ground connection to the inside wires. That would have been for the old 'party line' phones. Each phone had to have a connection to ground, as well and ring and tip conductors. The telco would put the ring voltage from either tip to ground or ring to ground. If you were on a 2-party system, then you would not hear the other party's phone calls coming in. Talking was still shared across the tip and ring though. (Worse was 4 party, but at least you'd only hear the other shared-side ringing.. then there was 10-party.. lol).
If you have an old party line phone still in use, it might need the ground wire . Not that the telco is still supplying the party line system, but the phone itself might still be modified to ring via ground.

The faraday cage thing sounds interesting. You wont be able to use radios etc inside there without extending the antenna outside of the cage (which of course then makes the cage less effective).