# Educate me on T1



## splatz (May 23, 2015)

The T1 signal is nothing like the ethernet signal. The best cable for the T1 IMO has two individually shielded 22AWG pairs. 



9720 | DataMax Multipair T1, E1, xDSL – 22 AWG, 2 pair, unshielded with shielded pairs, PVC, Beige | Quabbin Wire & Cable












This is best terminated in a screw terminal jack, most of the cat 5e / cat 6 jacks are not made for 22awg. But with that said, I have extended many T1's with existing cat 5e cabling, it's a very common practice. These days a lot of T1's start at a card in a cabinet on the customer's premises, with fiber back to the telco. But T1 was in common use before fiber to the customer's premises was commonly available, and still is often delivered over voice grade copper from the telco to the customer premises. In other words it goes miles over cable worse than cat5e.


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## Navyguy (Mar 15, 2010)

T1 was the Telco's answer before fibre became to be more common. The "speeds" with T1 are not great compared to copper*, but are rock solid normally. Still lots of them around in use, especially up here where fibre is still pretty much in it's infancy.

There are a lot of hardware options for T1 and matching hardware at both ends seems to be the best option, that is why for the most part the service provider supplies and installs the hardware. The cable for extending the T1 should be shielded, so I agree with @splatz, but once you leave the "box" (which is just a dedicated DSL line in reality) you are just into your network and your standard limitations of distance, noise, interference, etc apply.

Cheers
John

Edit - just reread my post - it should have said "not great compared to fibre"


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## Stuff (Oct 14, 2012)

Probably nothing for you to fix as problems are on the telco side. It's been years since I dealt with T1s and I don't remember for sure but think we even used Cat3 with RJ45s without issue to the CSU/DSUs used for data circuits (No RJ48s or shielded cable for us!). Normally you have a smartjack at each location where the telco converts the T1 to a RJ45. They can log in and check error counters as well as do loopback testing. Open a ticket and give them a window for intrusive testing. What's nice is that they can send a signal remotely to set the CSU/DSU to loopback for their testing, then tell you if it is an inside wiring issue.

The CSU/DSUs should provide counters you can see. For T1s someone needs to be the clock source. The telco normally is but with true point-to-point you need to configure one end to supply clocking or get strange intermittent problems.


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## mburtis (Sep 1, 2018)

So I did some poking around at one plant today. CAT 5E is being used to go from the phone companies card probably 200 ft across the building to a jack. From there a short Cat 5e cable runs to the SCADA computer. Took some pictures. Is there anything anybody sees that could be improved? Would upgrading the wire across the building be a good idea? Our network cabling after the computer is a complete mess so I'll work on cleaning that up as well.


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## mburtis (Sep 1, 2018)

So the more I read the more I don't know. Is the card doing the converting magic so it's just a regular ethernet network after that point?


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## LARMGUY (Aug 22, 2010)

All I know about the cards is when I was working at Southwestern Bell on their access control, each node had a T1 line. Frequently the "fix" was just to pull the card in the picture above and reinsert it effectively rebooting the card. This would usually bring back the lost comms to the node and the panels would start a fresh download. About a 15 to 30 minute service call.


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## emtnut (Mar 1, 2015)

mburtis said:


> So the more I read the more I don't know. Is the card doing the converting magic so it's just a regular ethernet network after that point?


It's a standard Ethernet port, but you need to know the service providers setup info to use/troubleshoot it.
(_edit_ you would also need to know the network setup from IT to be able to get on that network, and any static IPs of the T1 and any routers)

The T1's at my work that were for the corporate network, it was ONLY IT staff that had the info, and log in.

We had T1's on our own infrastructure on our separate network, so we supplied and installed the T1 bridges and knew all the set up.

I'd talk to your IT guy, and see if he can help you out. Where I was, I couldn't even call the Service Provider to troubleshoot the corporate lines, had to be on a 'list'.


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## splatz (May 23, 2015)

mburtis said:


> So the more I read the more I don't know. Is the card doing the converting magic so it's just a regular ethernet network after that point?


What comes out of the card is a T1, not ethernet. The card has an eight position modular jack, same as an ethernet device. It goes into a CSU/DSU (channel service unit / data service unit). Originally this was a modem sized device, and there was usually a big honking serial cable with a V.35 connector. Now, the CSU / DSU is usually either built into the router or an add-in card in the router. The router is the go-between device. 

There are CSU/DSU cards for PCs that would allow you to connect that T1 directly to a PC or other device like a PBX, but usually it goes to a router which bridges between ethernet and the T1 connection.


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## mburtis (Sep 1, 2018)

This is on a point to point data circuit between 2 water plants. Right now nobody is really in charge of managing it. What was confusing me was that this line runs straight to the SCADA computer so I wasn't sure if the phone company card was doing the csu/dsu function or if it was built into the computer. At the other plant it runs to the same switch that the ethernet control network uses. So technically cat 5 is a poor choice to run this across the building.


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## splatz (May 23, 2015)

mburtis said:


> This is on a point to point data circuit between 2 water plants. Right now nobody is really in charge of managing it. What was confusing me was that this line runs straight to the SCADA computer so I wasn't sure if the phone company card was doing the csu/dsu function or if it was built into the computer. At the other plant it runs to the same switch that the ethernet control network uses. So technically cat 5 is a poor choice to run this across the building.


Are you sure that the first device at the other plant is a *switch *not a router? If so those cards are not what I think they are and your service is not really T1, you have some ethernet handoff service, which may be at T1 speeds, but it's not a T1. I can't see the writing on the cards so who knows. 

If it is some kind of ethernet service, you might be better off buying dry copper from the telco - this used to be sold as a "burglar alarm circuit" a lot of places - and using your own extenders. 

BTW, there is a cover that's supposed to go over those exposed circuit boards, is that laying around somewhere? I would want that cover on the electronics.


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## mburtis (Sep 1, 2018)

Happen to be on call this weekend so I took a look at the other plant. From my knowledge the connection at this plant is phone company card to obsolete Cisco gigabit switch, then to the computer. 

















Also we have the covers for the cards. I just took them off to look at the wiring and take pictures.


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## mburtis (Sep 1, 2018)

Actually traced the wire out and I was wrong. The cable from the card actually runs into the control cabinet and goes into a now non supported Cisco 1841 router with the csu/dsu card. From there it runs into switch with a bunch of crap on it, then over to a wall jack, to another switch, and then finally to the computer. We have another one of these Cisco routers out at the other plant that I looked at a couple days ago, but I could have swore that the cable from the phone company card ran straight to the computer out there. I'll have to look at it later today.
















At least I understand somewhat what is going on now. I couldn't figure out how it was working without finding the csu/dsu. Other than generally being a cluster does anyone see anything specific that could be improved on the physical installation? Upgrade wire, upgrade switches/routers, etc.


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## splatz (May 23, 2015)

You're right that's a pretty mickey mouse setup. The cat 5 cable from the smart card / demarc to the router is not likely a major problem if it's a good cable properly run. However T1 does not reject noise the same way ethernet does, if this is running near sources of interference it could be an issue. 

It looks like it's terminated in plugs, I'd terminate it in jacks, and use *factory *patch cords from the jack to the smart card, and from the jack at the other end to the T1 card in the router. 

The cisco routers have quite a bit of logging and diagnostic info for he T1 but it's a pretty steep learning curve to work with Cisco routers. 

I would not be too quick to conclude that the problem is the T1 itself. There are a fair number of places this could be going wrong.


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## mburtis (Sep 1, 2018)

It seems like there are about 14 components that could contribute to the various drop outs etc that we experience. My goal is to learn enough that I can at least sort through and shore up our end of it. At least that way I can have more confidence pushing on the phone company when we have problems.


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## splatz (May 23, 2015)

mburtis said:


> It seems like there are about 14 components that could contribute to the various drop outs etc that we experience. My goal is to learn enough that I can at least sort through and shore up our end of it. At least that way I can have more confidence pushing on the phone company when we have problems.


That's understandable but that is a lot to learn, and it's an IT guy's job. It might be better to stay in your lane, and hold your IT department to figuring it out. You can't blow yourself up playing with this IT, but you can certainly hose your network and you could get in hot water if there's a breach, which your tinkering may or may not have anything to do with.


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## emtnut (Mar 1, 2015)

mburtis said:


> It seems like there are about 14 components that could contribute to the various drop outs etc that we experience. My goal is to learn enough that I can at least sort through and shore up our end of it. At least that way I can have more confidence pushing on the phone company when we have problems.


I often called the phone company first, or after cursory checking things.
They can easily do a loopback check and also check signal levels/errors etc.
There was never a charge, unless you requested them to come out, and it ends up being a problem on your end.

A butt set is a good basic test tool. Make sure it has high impedance mode, and listen to the line. Often I found ground hums (usually bad carbons)


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## mburtis (Sep 1, 2018)

This is a point to point data circuit, the internet and all the normal IT stuff is completely seperate so I'm not to worried about causing any security breaches or getting in to much trouble. All the ethernet stuff is connections to PLCs, radios, HMIs, etc. Worst that will happen is something will quit talking. However as you point out I have no desire to be an IT guy and I really don't think I have any desire to learn how to configure/monitor the router. When I say shore up our end of things I mean mostly a big dose of cable management and maybe upgrade/consolidate switches and generally clean up the physical install so it's not so confusing and messy. At least be able to see if the blinky lights are blinky or not.


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## magicone2571 (Apr 29, 2021)

mburtis said:


> This is a point to point data circuit, the internet and all the normal IT stuff is completely seperate so I'm not to worried about causing any security breaches or getting in to much trouble. All the ethernet stuff is connections to PLCs, radios, HMIs, etc. Worst that will happen is something will quit talking. However as you point out I have no desire to be an IT guy and I really don't think I have any desire to learn how to configure/monitor the router. When I say shore up our end of things I mean mostly a big dose of cable management and maybe upgrade/consolidate switches and generally clean up the physical install so it's not so confusing and messy. At least be able to see if the blinky lights are blinky or not.


If you're having issues get your carrier involved. There's a lot of different tests they can do on the line to pinpoint issues. Most likely the pair on the carrier side is bad. 

If needed to build a loop back plug, pins 1 to 4, 2 to 5 on a standard rj45 mod end. Just loop the 2 wires and crimp. You have a loopback now.


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## mburtis (Sep 1, 2018)

So yesterday we got some monitoring set up on our t1 line. There was already the base programming in the plc as there was messages being monitored for watchdog alarms etc. The outside programmer and I just had to figure out how to utilize it and log it. Been running a day and so far we have seen 4 failures for a total of over 4 min


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