Cat 6 for telephone

[drozwood90]

In the your mileage may vary department, plugging in RJ11 plugs into RJ45 jacks over time may bend the springs on some of the side pins so they no longer work well as Rj45 jacks. A moot point if you never move things around of course. And it does not happen instantly, or even all the time. But businesses who did this a lot in the early days often found themselves replacing a lot of jacks later, and many (well, at least ones I do) will wire the phone with a real RJ45 plug instead. Cost is negligably different, and I heartily endorse just wiring everything with RJ45 where you can.

I agree with this. When I "patch" RJ11 to RJ45 I typically make up an adapter.

So, in the RJ45 jacks, there are only CAT5/5e cable ends. Then the other side is crimped with RJ11 to plug into...say a phone or whatever. Also useful at the patch panel.

--Dan

 

[drozwood90]

What happens if you use rj45 jack for a telephone and someone plugs an ethernet cable into it by mistake? Seems to me that a telephone ring which has substantial voltage would fry your computer/router/whatever. I've never measured a ring voltage, but I have gotten shocked by it before. If it can shock me, it has to be able to do damage.

Should be -45V to -75V as the TIP is pretty high. If you plug that into an ethernet jack on an ethernet card, shouldn't do anything. Ethernet is isolated by transformers...something to do with lightning codes and what-not.

Sorry if I'm a bit vague...I've not had to design an ethernet board in a while. I know POE was a PITA due to the layout of the boards...dang lightening!!

--Dan

 

[drozwood90]

also, it is one of the reasons the blue wires are where they are in the ethernet wire layout. They are the wires typically used for phone. Think about plugging an RJ11 in to a RJ45 wall jack...when it finally gets in there, the 4 RJ11 wires touch the 4 center RJ45 wires.

I had read that it was designed like that on purpose...

 

[tmbrown97]

Yup - I've been doing telecom for many, many years (part of my regular duties). There's a reason the blue/blue-white are still the center pair... that's tip/ring on the main phone line. The next pair is actually on either side - Green-white/green is the next pair on either side... that's typically line 2, reversed polarity. Ethernet was designed to kinda work around these and that's why it shares similarities. In fact, until GigE, Ethernet only used 2-pairs, and the other two could be used for phone, or dual-ethernet connections.

Ring voltage is ~70 volts. i don't know the amps, but I've been hit with that more times than I can count. It won't kill you, but it's not fun. In fact, I'm kinda the a-hole boss who teaches his employees about this by calling the phone numbers people are working on.... part of the whole learning process. In newer facilities, you can disconnect the test jack while you're working; in older places you just pray nobody rings in!

Oddly this is one of those things I became a true expert on when I was 12yrs old - I was the man of the house, so it was my job.

 

[apostolakisl]

Yup - I've been doing telecom for many, many years (part of my regular duties). There's a reason the blue/blue-white are still the center pair... that's tip/ring on the main phone line. The next pair is actually on either side - Green-white/green is the next pair on either side... that's typically line 2, reversed polarity. Ethernet was designed to kinda work around these and that's why it shares similarities. In fact, until GigE, Ethernet only used 2-pairs, and the other two could be used for phone, or dual-ethernet connections.

Ring voltage is ~70 volts. i don't know the amps, but I've been hit with that more times than I can count. It won't kill you, but it's not fun. In fact, I'm kinda the a-hole boss who teaches his employees about this by calling the phone numbers people are working on.... part of the whole learning process. In newer facilities, you can disconnect the test jack while you're working; in older places you just pray nobody rings in!

Oddly this is one of those things I became a true expert on when I was 12yrs old - I was the man of the house, so it was my job.

Standard ethernet doesn't use the center 2 (blues), but it does use the next 2 (the greens), so if you had a 2 line phone system and plugged ethernet into it, you would get 70v on the wires which are actually connected to circuitry when someone called line 2. So, you are saying that devices that accept ethernet are required to protect against overvoltage on there?

And I too believe I might have been about 12 when I got my first telephone ring zap. Even dial tone voltage will buzz you a little sometimes.

 

[tmbrown97]

To be completely honest, I'm not positive if protection against voltage on Line2 is protected against... I think I read something that said it was, but don't know 100%. I *know* people plugged ethernet into the occasional PBX port around my old office - happened all the time honestly... never heard of a fried NIC from it; then again, in an office you rarely have 2 POTS lines; it's either a digital PBX or a single fax/conference line... but most of our business laptops for at least the last 5 years have been coming with gigabit NIC's which do use all the pairs, so they'd be using the blue pairs as well... and still, no failures seen.

I do know I've been running things this way for close to 10 years now in some quite large commercial facilities, and haven't had one single issue result, despite people plugging things into random ports. And in my current 5yr old master-planned community of 3000 homes, it's how every house was wired.

 

[drozwood90]

Yup - I've been doing telecom for many, many years (part of my regular duties). There's a reason the blue/blue-white are still the center pair... that's tip/ring on the main phone line. The next pair is actually on either side - Green-white/green is the next pair on either side... that's typically line 2, reversed polarity. Ethernet was designed to kinda work around these and that's why it shares similarities. In fact, until GigE, Ethernet only used 2-pairs, and the other two could be used for phone, or dual-ethernet connections.

Ring voltage is ~70 volts. i don't know the amps, but I've been hit with that more times than I can count. It won't kill you, but it's not fun. In fact, I'm kinda the a-hole boss who teaches his employees about this by calling the phone numbers people are working on.... part of the whole learning process. In newer facilities, you can disconnect the test jack while you're working; in older places you just pray nobody rings in!

Oddly this is one of those things I became a true expert on when I was 12yrs old - I was the man of the house, so it was my job.

it's not measured in current. It's measured in RENs
http://en.wikipedia.org/wiki/Ringer_equivalence_number

 

[drozwood90]

Standard ethernet doesn't use the center 2 (blues), but it does use the next 2 (the greens), so if you had a 2 line phone system and plugged ethernet into it, you would get 70v on the wires which are actually connected to circuitry when someone called line 2. So, you are saying that devices that accept ethernet are required to protect against overvoltage on there?

And I too believe I might have been about 12 when I got my first telephone ring zap. Even dial tone voltage will buzz you a little sometimes.

they are required to be isolated. If you put a static 70V on there, it won't do anything since they ethernet is DC isolated.

And if I am remembering properly, it's actually -70V. I recall designing a flyback circuit to power one of those buggers for an ATA (VOIP analog telephone adapter). was shooting for -75V.

--Dan

 

[drozwood90]

There we go...that's why, it has been a long time since I've had to design one of these things...

http://en.wikipedia.org/wiki/Telephone

"The wire's voltages are negative compared to earth, to reduce galvanic corrosion. Negative voltage attracts positive metal ions toward the wires."

 

[drozwood90]

neat, that article explained about the tip being -48V. Nice refresher! so, it's -48V to -70V. I think we made our ATAs -45 and -75, as the flybacks were easier to design with off the shelf parts (i.e. 10ohm resistor to ground, vs. 10.2ohm type of situation). When you talk quantities of 10,000 resistors, it is a whole different ballgame trying to order parts.

 

[apostolakisl]

Nice info guys.

Still, I'll put the rj-11 keystone on my phone jacks. They cost about the same and the phones just plug in easier since they have rj11's already. Plus, no questions from my somewhat technologically challenged staff such as "I plugged the computer in to the thingy on the wall, why doesn't it work"

 

[drozwood90]

haha, not a problem! I'm just glad I was finally able to answer some questions on this place! I always feel like a bit of a heel not being an "expert" on anything here. What I do for a living tends to be nothing like what's on this board.

--Dan

 

[Alexbrown012]

I'm in the middle of a remodel and have run Cat 6 and RG6 throughout my house. The electrical inspector was in my house recently inspecting the electrical system and told me that the Code will not allow me to use Cat 6 for telephone.

We are cord cutters and did not see the point of running Cat 3 that will never be used. I have a distribution panel where phone service can be distributed if we ever need the service using the per existing Cat 6 cable.

Can someone point me to something in the electrical code (we use NFPA 70), etc that I can use to show the inspector that Cat 6 is acceptable? I live in south florida if it matters.

Thanks for your help.

 
Hoping till now you got recovered from this issue !!!. Although that is the nearly all bizarre point I've got heard. It's not possible to use "better" wire involving similar form? 

I would call up this constructing team in addition to dig more deeply into that particular wondering your ex showing you where it can be "not" authorized.

 

[Del91574]

The IRC code as written specifies "at least 1 readily accessible jack" wired in a home, not installed on a joist or at the panel itself....typically the install goes back to the old Bell system rules, jack in the kitchen (and if you want to get paid on a works project, thats where it must be). Code does not dictate the rating on the cable other than the rating of the insulation, the FCC mandated the minimum of Cat 3 for voice purposes.

Thanks for the advice, I think I am going to go with running a single line of Cat 3 phone wire to a location closest to where the phone service enters the house.