T1 wiring question - two circuits over one CAT5 cable?

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T1 wiring question - two circuits over one CAT5 cable?

Postposted on Thu Mar 29, 2012 3:13 pm

I am in the process of planning a T1 upgrade (1.5MB > 3.0MB) to my company's seperate manufacturing facility.
Currently we have a single T1 data connection, with Adtran Netvanta 3205 routers on each side.
I have ordered (2) Adtran 1202872L1 modules for these existing routers to allow a 2nd T1 to be added giving us 3MB btwn buildings.

I currently have a single CAT5e cable between the Smartjack and the NetVanta. Looking at the wiring for T1's:
http://www.bohack.com/2009/05/t1-rj-48c ... mart-jack/
This shows that only 4 of the 8 pins are actually used.

My question is: Can I just use the remaining four pins for the 2nd T1 so I don't have to run another cable from the smartjack to the router?

Or is there some reason why that's a bad idea?

TIA
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Thu Mar 29, 2012 3:36 pm

Pins 1,2,3, and 6 are the transmitting pins (typically). Your plan may compromise protection against attenuation (EMI/Crosstalk).
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Thu Mar 29, 2012 3:39 pm

Cabling for DS1 circuits need to be individually shielded pairs! CAT 5e and CAT 6 cable is NOT for DS1 circuits! Category cables are for ETHERNET use. ETHERNET transmission is NOT DS1 transmission. Just because uninformed people do it, doesn't make it the right way to do it.

In short, DS-1 systems are far different from LAN Category 5.

Copper cable used to transmit T-1 and T-3 signals has been available for many years. A typical design is 2 pair 22AWG with foam skin insulation, each pair shielded, with 100 ohm impedance. These are commonly known as ABAM telephone cables. The physical size of these cables requires termination with DB-15 connectors, punch-down hardware or mechanical terminal blocks. These older cable designs and their termination systems were developed for T-1 applications when they were confined within a telephone company's central office facility.

Using shielded Cat3 looks to be your best bet.
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Thu Mar 29, 2012 4:10 pm

http://www.tek-tips.com/viewthread.cfm?qid=1630733
I see what you did there, Gleek. :P

FWIW, we've been using CAT5 for T1, SDSL, Ethernet, and phone lines here at work for YEARS without an issue.

http://newsgroups.derkeiler.com/Archive ... 00053.html

That guy says it's fine. As do others I've found. I have a call into US Signal for their advice.

I was wondering if anyone has experience personally doing this - thanks. :) I think it's about 75-100 feet btwn smartjack and routers on one end, and only about 30-50 feet on the other end.
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Thu Mar 29, 2012 4:15 pm

FroBozz_Inc wrote:http://www.tek-tips.com/viewthread.cfm?qid=1630733
I see what you did there, Gleek. :P

That's fine. Sometimes I copy/paste things without credit. Google works great eh?

FroBozz_Inc wrote:FWIW, we've been using CAT5 for T1, SDSL, Ethernet, and phone lines here at work for YEARS without an issue.

http://newsgroups.derkeiler.com/Archive ... 00053.html

That guy says it's fine. As do others I've found. I have a call into US Signal for their advice.

It may work for some, but not for all.

FroBozz_Inc wrote:I was wondering if anyone has experience personally doing this - thanks. :) I think it's about 75-100 feet btwn smartjack and routers on one end, and only about 30-50 feet on the other end.

Um. I -HAVE- personal experience doing this. I've routed/connected/installed/troubleshooted MANY T1/T3 dsu/csu/mux/etc's in my time dude. kthx.
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Thu Mar 29, 2012 4:20 pm

My point still stands as well.

Taking a single CAT cable and splitting the pins in the manner suggested increases the likelyhood of head end attenuation and may compromise the EMI and crosstalk protection along the length of the cable as well.
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Thu Mar 29, 2012 4:24 pm

Ryu Connor wrote:My point still stands as well.

Taking a single CAT cable and splitting the pins in the manner suggested increases the likelyhood of head end attenuation and may compromise the EMI and crosstalk protection along the length of the cable as well.

Which is pretty much the same thing I posted, even if it weren't -MY- words verbatim.
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Fri Mar 30, 2012 7:17 am

Thanks for the input guys.
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Fri Mar 30, 2012 8:28 am

You'd really think that a twisted pair cable designed to carry full-duplex 1000 Mbit/sec traffic would be able to handle a measly 3 Mbit/sec!

That said, I agree with the other replies. For critical business infrastructure, you really need to use the proper cabling... if something goes wrong, it's your a** on the line!
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Fri Mar 30, 2012 12:24 pm

I haven't heard back from the carrier yet.
This is an illustration of what I *thought* I wanted to do:
http://www.cabling-design.com/reference ... plit.shtml

Since I'll likely do it by the book though - this is the wire I'm looking at for my double T1 circuit:
http://greatwire.com/Catalog/Central-Of ... ble/20176/

Edit: heard back from our telco vendor:
The proper way to terminate a T1 beyond the Dmark is using T-Span Cable. It’s what we use when quoting the extending of a Dmark ($3.60 per foot)
Some use Cat5
Others use Cat3

Bottom line is it “Should” work, but in this business no hard and fast rules exist.
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Fri Mar 30, 2012 1:34 pm

Well it's not my profession, however being an engineer I love standards.

I believe the toughest or highest standard when it comes to G-P telecommunications cable is the ISO 11801, it would be good if your cable is rated or approved to this standard, as it exceeds the tia/eia 568 standard.
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Sat Mar 31, 2012 8:39 am

just brew it! wrote:You'd really think that a twisted pair cable designed to carry full-duplex 1000 Mbit/sec traffic would be able to handle a measly 3 Mbit/sec!

Ethernet runs at +-2.5V whilst I believe T1 to run at -48V although that may be just the external side, it has been a while since I did anything other than Ethernet.
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Sat Mar 31, 2012 9:18 am

-48V is the standard power supply voltage for telco equipment, it has (almost) nothing to do with the transmitted signals. AFAIK the only time high(ish) voltages are used over the lines is to send the ring signal on analog voice lines (for compatibility with legacy telephones having electromechanical ringers).

Edit: 48V signaling at the sort of frequencies used for T1 transmission would create an enormous EMI problem as well.

Edit 2: Speaking of legacy equipment, I remember reading somewhere that the telcos have maintained backward compatibility with analog phones going back more than 100 years. You can theoretically take an antique crank-style phone, splice a modular plug onto it, and plug it into your present-day POTS phone line. Turning the crank will get you an operator, because it generates an outgoing signal on the line that is close enough to dialing '0' on a rotary dial phone for the equipment at the switching center to recognize it!
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Sun Apr 01, 2012 9:21 am

http://www.inetdaemon.com/tutorials/tel ... arrier/T1/ suggests +12V or -12V and 0V but I thought it was more than that. I did a training course on a Siemens SMX 2100 about 12 years ago and I remember that the real telco guys were concerned they might get shocked by all the bare terminals labelled T1 until the instructor pointed out that they were not real T1s but at a lower voltage. The instructor also said the 1.5Mb/s of a T1 was based on the distance between the telco manhole covers in New York - they thought New York would use the most T1s and they could throw a repeater down each telco manhole. Given the tech at the time they ended up with 1.5Mb/s as what was a safe signal to transmit that distance.
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Sun Apr 01, 2012 10:12 am

notfred wrote:http://www.inetdaemon.com/tutorials/telecom/t-carrier/T1/ suggests +12V or -12V and 0V but I thought it was more than that. I did a training course on a Siemens SMX 2100 about 12 years ago and I remember that the real telco guys were concerned they might get shocked by all the bare terminals labelled T1 until the instructor pointed out that they were not real T1s but at a lower voltage. The instructor also said the 1.5Mb/s of a T1 was based on the distance between the telco manhole covers in New York - they thought New York would use the most T1s and they could throw a repeater down each telco manhole. Given the tech at the time they ended up with 1.5Mb/s as what was a safe signal to transmit that distance.

Other references seem to indicate that the signal swing is even less, +/-3V.

However, I believe I've figured out where the high/low voltage confusion is coming from. Apparently a "real" T1 span can have the data signal riding on top of a 130V DC bias. This DC is used to power the repeaters. And yes, 130V will give you a nasty shock! (Sounds like it is the same basic idea as Power Over Ethernet, just much older...)
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Re: T1 wiring question - two circuits over one CAT5 cable?

Postposted on Sun Apr 01, 2012 9:29 pm

Ah, that would be it! Thanks.
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