fire alarm- phone line

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hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Like you said you are not in a rural area. Many places still do not have DSL because of distance. The only way we get high speed internet is via wireless sources.
Very true but we are not talking about DSL here. And if we were you probably would not want to use CAT5 for 700 feet due to the higher pair capacitance. With DSL every little bit helps.


-Hal
 

esobocinski

Member
Location
Ann Arbor, MI
Very true but we are not talking about DSL here. And if we were you probably would not want to use CAT5 for 700 feet due to the higher pair capacitance. With DSL every little bit helps.


-Hal

Hrm? Higher category numbers have *lower* pair capacitance: Less than 20 pF/ft for Cat 3, 17 pF/ft for Cat 5/5e, 15 pF/ft for Cat 6. Honestly, you aren't going to notice the capacitance difference at voice frequencies on an extension loop of 700 feet. Telco POTS engineers start to worry about capacitance at 15000 to 17000 feet.
 

Jhaney

Senior Member
Location
owensboro, ky
worrying about the last 700 or 1000 feet is not worth the effort, in this rural area we have pots working in the access of 30k feet, of course there is alot of buildout to make it work that far. As for Cat 3 or Cat 5, you need to consider if its worth it based on the fact that the phone company isn't running Cat 3 or Cat 5 now if it was behind a fiber based server system then yes Cat 5 would be the way to go.
As for placing the line in conduit, the only reason I could possibly see doing it was from physical damage but since it has been stated it's going to run in the ceiling I really wouldn't do more than the initial stub out unless forced too.
If the fire alarm system hasn't caught the fire before the phone line burn in two then your really having a bad day.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Hrm? Higher category numbers have *lower* pair capacitance: Less than 20 pF/ft for Cat 3, 17 pF/ft for Cat 5/5e, 15 pF/ft for Cat 6. Honestly, you aren't going to notice the capacitance difference at voice frequencies on an extension loop of 700 feet. Telco POTS engineers start to worry about capacitance at 15000 to 17000 feet.
I have no idea where you got those numbers from. You got me looking at several manufacturers and none publish specs for pair capacitance on any of their cables. So unless insulation thickness is increased (which I don't see) common sense dictates that capacitance increases as the wires are twisted tighter and tighter.

Also, I was talking about it's possible effect on DSL not POTS.

-Hal
 
It all comes out about the same:

http://communications.draka.com/sites/eu/Datasheets/SuperCat5_24_U_UTP_Install.pdf
Capacitance at 800 Hz Nom. 52 nF/km

http://www.westpenn-wpw.com/webcatalog/BULK CABLES/LAN-NETWORKING/CATEGORY_5E.pdf
Nom. Cap.14 pf/ft*

http://www.lappusa.com/Spec_Template3.asp?nGroupID=5600
Nominal Capacitance: 17 pF/ft

Either way, I wouldn't worry about a few hundred feet of CAT5 cable carrying DSL. CAT5 is better for high frequencies than generic OSP cable, and having done a DSL demo over barbed wire, it will run over almost anything.
 

esobocinski

Member
Location
Ann Arbor, MI
I have no idea where you got those numbers from. You got me looking at several manufacturers and none publish specs for pair capacitance on any of their cables. So unless insulation thickness is increased (which I don't see) common sense dictates that capacitance increases as the wires are twisted tighter and tighter.

Also, I was talking about it's possible effect on DSL not POTS.

-Hal
Hal, my numbers came from the ANSI/TIA/EIA-568 standard, so they're maximums. Most manufacturers do slightly better so that they can also meet ISO/IEC 11801 requirements for Europe.

You're right that simply twisting tighter will increase capacitance. To meet the tighter spec requirements for higher EIA category numbers or IEC classes, manufacturers need to use different insulation materials that have lower dielectric constants to counter that effect and then get additional reduction.

I knew you were talking about DSL and not POTS. I wanted to correct it anyway since people do find these threads later and use them as reference. :)
 

MAK

Senior Member
Perhaps a bit harsh, but a little thinking before asking a question goes a long way.:happyyes:

-Hal
I asked because of the post that said run cat 3 instead of cat 5 because of the extra twists make the cable longer than 700 feet. It seemed to indicate that more than 700 feet was undesirable length of cable.

Also I would ditch the cat.5 and run cat.3, the extra twists in cat.5 make the electrical length of the run longer than 700 feet. The telco provides dial tone on cat.0 so runing cat.5 gains nothing.

I was wondering why someone would run cat 3 vs cat 5 for POTS line. Seems inconsequential. From our supplier cat 3 is more expensive than cat 5E. That's why i asked. :thumbsup:
 

massfd

Member
I was wondering why someone would run cat 3 vs cat 5 for POTS line. Seems inconsequential. From our supplier cat 3 is more expensive than cat 5E. That's why i asked. :thumbsup:
Funny, over in the telephone fourms they refer to sparkys who run cat.5 for telephone (not VOIP) as HACKS but I did see 1 telephone fourm member post here and he never mentioned it.

Cat.5 was not designed for POTS service, it's a shame that the pricing has made proper telephone products more expensive than the data products, Guess it is the volume of sales.
 

esobocinski

Member
Location
Ann Arbor, MI
Cat 3 wasn't designed for voice either. It was designed for ISDN (channelized digital telephony), and Cat 3 was encouraged for new POTS installations so that those lines could be converted to ISDN later. ISDN didn't get much deployment in North America, but all that Cat 3 was useful when DSL came along. The EIA/TIA specs folks intentionally made all "categories" to be POTS-compatible, and electrical characteristics at voice frequencies are basically identical for anything from Cat 3 to Cat 6a.

There was never any argument for using Cat 3 instead of Cat 5 or 5e for POTS except for cost. Now that the cost is inverted, there's no reason at all. Any of those telco forum guys who claim Cat 3 is "more proper" are full of it. Put them in the same box of luddites as anyone still wiring television with 300 ohm twin-lead, even if they're still using antennas.
 

hurk27

Senior Member
Cat 3 wasn't designed for voice either. It was designed for ISDN (channelized digital telephony), and Cat 3 was encouraged for new POTS installations so that those lines could be converted to ISDN later. ISDN didn't get much deployment in North America, but all that Cat 3 was useful when DSL came along. The EIA/TIA specs folks intentionally made all "categories" to be POTS-compatible, and electrical characteristics at voice frequencies are basically identical for anything from Cat 3 to Cat 6a.

There was never any argument for using Cat 3 instead of Cat 5 or 5e for POTS except for cost. Now that the cost is inverted, there's no reason at all. Any of those telco forum guys who claim Cat 3 is "more proper" are full of it. Put them in the same box of luddites as anyone still wiring television with 300 ohm twin-lead, even if they're still using antennas.
Another benefit using a twisted pair cable when you had multi-lines going through adjoining pairs was cross talk, I can remember this problem in our office as you could hear other conversations on the other lines not clearly but it was there, then we installed twisted pair and this problem went away. the fax machine or dial up modems would drive us crazy as it was much louder.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Cat 3 wasn't designed for voice either. It was designed for ISDN (channelized digital telephony), and Cat 3 was encouraged for new POTS installations so that those lines could be converted to ISDN later.
I don't lnow where you came up with that bit of trivia. CAT3 was the original ethernet after thin net (RG58 coax and BNC connectors) fell out of favor because UTP was easier to work with. There was a CAT4 after that. CAT3 was "encouraged" and still is for POTS because it is a twisted 4 pair cable and that makes it useful for premise wiring handling more than one line which was becoming more and more common at that time. If you put two lines on a 4 conductor J/K station wire that has parallel r/g/b/y conductors you will have a crosstalk problem. 4 conductor station wire was designed for one line and 10VAC from a plug-in transformer to light the dial light on Princess phones.

Multi-line business systems back then used 6, 12, 25 and multiples of 25 pair cable that was twisted pair but there was no CAT specification then. That only came about when data started using UTP cable.

There was never any argument for using Cat 3 instead of Cat 5 or 5e for POTS except for cost. Now that the cost is inverted, there's no reason at all.
The cost may be inverted at the usual sparkie or IT hang outs because CAT5 is all their customers know to ask for so that's all they stock. If you ask for CAT3 it's in limited supply or special order so it's going to cost more. Telecom supply sources will have normal prices. Also, if you look at the cost difference between CAT3 PLENUM and CAT5e or CAT6 PLENUM you will see that the difference is considerable.

Any of those telco forum guys who claim Cat 3 is "more proper" are full of it. Put them in the same box of luddites as anyone still wiring television with 300 ohm twin-lead, even if they're still using antennas.
Spoken like a true IT guy who never has seen or done a proper telecom installation. We all must be wrong, right? We don't use patch panels or 110 blocks. Our cross connect fields are 66 blocks and if you want to spend twice as much time untwisting pairs, not to mention the damage it does long term to your hands as well as the cost difference for plenum listed cable go right ahead. We aren't luddites, rather you IT guys need to get you heads out of your you know what and understand that the world doesn't revolve around you.


-Hal
 
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