Is a T1 a safe replacement for POTS???? 4

[FIREANDSECURITY]

If I understand the T1 correctly, a digital signal is sent from the Central Office on 1-pair of cables to the business. A DSC/CSU at the premises will convert it to either 24 loop start voice circuits, or data circuits, or a combination of both. The DSC/CSU provides dial tone 48volts to the lines needed for a analog phone.
My question (1) is if the 1-pair phone line is lost from the central office to the DSC/CSU, will the DSC/CSU stop providing voltage on the analog phone side?
Question (2) Can the DSC/CSU fail yet still provide the 48 volts onto the analog phone pair?




A DSU/CSU divides the 1-pair line in into 24 voice, data, or voice/data circuits.

 

[Dexman]

A typical T1 uses 2 pairs of wires. 1 pair is for transmit and the other is for receive.

There are multiple ways to demux a T1. Channelbanks, CSU/DSUs and T1 cards built into phone systems are all examples.

The service provider can supply dialtone except in the case of ISDN service. If you use ISDN, dialtone would be generated by the telephone system itself.

If either of the 2 pairs went open, the T1 itself would be unusable as the CPE would either detect an open condition or it would see a remote alarm from the provider, depending on which pair went open.

My feeling is that it is always a good idea to have POTs lines available so that, in most cases, there will be some sort of redundancy available should the T1 either become unusable or overloaded.

Of course, if a pole, carrying T1 and POTs cables were to fall over, the only service available would be cell phones.

 

[ronromano]

Yes

 

[PERRYPJ]

I WILL HAVE TO SAY YES ALSO, PLUS THE SAVINGS YOU WILL GET THE BRAKE EVEN POINT IS 12 CHANNELS OR TRUNKS AFTER THAT THEY ARE ALMOST A FREE-BE

OLD ROLMEN WORKING ON NORTELS

 

[jml2665]

what is your application for the analog stations? based on your handle if you are looking for elevator/alarm type applications please check with yout local/county/state codes as I would think they will have very specific rules on what sort of circuits are required.

 

[FIREANDSECURITY]

My application is using a T1 as the only source of monitoring a fire alarm system. NFPA appears to prohibit its use because 2-different loop start lines are specifically indicated as required with voltage being supplied by the central office. There is a provision for alternative transmission equipment but it does not reference T1s. The local fire marshall believes it is acceptable per conversations with her boyfriend in the telecom business. The customer has been told by the phone service provider that they are using it in other areas in Texas. Im concerned that there may not be any safeguards specifically indicated in the fire codes.
Im not against the T1, but I must believe it meets code and not just because the AHJ says its ok. So I am really looking for operation ability of the T1 equipment.
If the T1 CSU fails is there still a 2nd way for a signal to be transmitted within the T1 equipment?
Can a 24 hours back up power supply be monitored by the T1 to provide a output relay for sinnalling the batteries are low?
Can it signal when 120vac power is lost?
Can the T1 signal when the incoming pair is lost?
Can it signal when the outgoing pair is not communicating with the public phone network?
Will all T1 equipment operate as above?
Thank for all comments on this issue.
Louis

 

[ISDNman]

I think you are right, the T1 channel bank does not meet the intent of the regulations (that Telco battery and equipment should be (in the majority of cases)be more reliable than than a random channel bank and a random UPS.)Also, in theory POTS offers more redundancy.

That said, an ever growing number of POTS lines are delivered from line concentrators (SLICs) and in therse cases are NOT powered by CO battery. Maintaining the remote terminals and there battery has in some case been reduced to the point where only a few hours of battery backup is available in real practice.

If you were to go this route you would want to find chanel banks that meet Belcore standards for CO operation and run your own battery plant.

Good luck

 

[GMgerry]

It seems everyone is wrong here. A CSU/DSU will not provide dial tone or -48vac or 24 channels. It is an interface that the carrier can test through the smart jack. You need to add a channel bank in order to break out 24 analog channels. You will also need a channel back that breaks out analog trunks and pass data, a drop and pass CSU. On a T-1 or PRI the central office sends one pair of data and another pair of power. This will power the smart jack and provide a live T-1/PRI interface. Than you go to a CSU/DSU than to a PBX or channel bank.

I do not recommend using a T-1 for critical services such as fire alarm, security systems, etc. or any other equipment that is basically a "Life Safety" system. If you’re looking to provide a low cost analog solution with digital service you may want to look into pricing of a digital card for the system your interfacing to. The performance of a T-1/PRI really shines verses POTS lines.

 

[ronromano]

Everyone? I don't believe I commented on CSU/DSUs.

 

[LkEErie]

So now we got to the same page. T1/PRI to a CSU/DSU to a Channel Bank or PBX to a PBX Probably using a Channel bank to break out a POTS line or 2 for alarms? The Smart Jack sits on the T1 line and it could be one or two pairs depending on if the delivery is normal or by SDSL.

The OP has a decision to make, because, while the derived lines on a channel bank are not "copper to the C.O." the CO lines might not be either. Now you get to pick your backup systems. A well backed up channel bank might have more redundancy than the telco privide SLIC and restoration of service would be more of a priority on the t than POTS.

Just a thought.

LkEErie

 

[jml2665]

seems we were all trying to help, how does it seem we were all wrong?

 

[oldtimerbob]

Fire alarm and elevator lines should be POTS and hooked up as direct to the BP as possible. Some alarms require a back up line also.
Seems to me you should check with your alarm company before you start making everything more complicated ( and they will know about the regulations in your area).
Good Luck,
Bob

Has been in the cabling business for about twenty years and is now the Sr PM for a cabling company located in the Los Angeles area.

http://www.globusinc.net

Also a General Class Amatuer Radio Operator.

 

[hawks]

Like oldtimer said I would check with your alarm company and/or Fire Marshall. They can tell you what is required in your area. Because I do know if it is not up to whatever the standard is you may have issues with your Insurance company also if you ever need it because of fire or break in.

 

[GMgerry]

Never wrong in helping, just the information was not stated correctly and may provide a bad understanding of equipment.

 

[FIREANDSECURITY]

Thanks everyone. I am the fire alarm company. The local AHJ is in favor of using the T1. My concern is I must meet State/NFPA 72 compliance. Its clear no one answering this ??? has used the T1 in this application.

 

[LkEErie]

The problem is that I have an agreement with my insurance company; I don't do fire or burglar alarms and he doesn't raise my liability premiums. So when you cite NFPA 82 I don't have a clue and don't need to know.

You're probably asking this in the wrong venue. Maybe Mike Holt's group might get you a more definitive answer.

LkEErie

 

[SYQUEST]

As long as the service is generally reliable, it would probably be acceptable. With the proper battery backup equipment, it should be just as reliable as the remote DLC that the Telcos use out in the field these days.

Having a second line for back up from the same DS1 would be no different from Telco doing it, because they would be provisioning lines from the same remote DLC, unless you could get them to use another route or DLC to serve the location for the other line.

In addition to following all other related codes that might apply. But the AHJ would have the last word on what they accept or not.

Lastly, I don't think it is a case of no one not using this method to communicate alarm system status. Quite the contrary, they probably have and did not realize they were. Especially with all the CLEC service out there now. This is what they have been doing since the late 1990s. They bring out a DS1, stick in a Channel Bank and provision dialtone. So it really is not new. I don't think anyone has really thought about it in the terms or description you presented in the opening post.

....JIM....

 

[gleaso]

I have installed loop start lines coming off of a channel bank to a few alarm systems here in Tucson and have never had a problem with them, in fact there is the advantage (aside from the savings to the customer)in that most of the T1 providers guarantee 99.99 percent uptime on their circuits and they will put that in writing. If a POTS line goes down it may be days befor you see a technician on site to repair it and the Telco is not going to rush the repair just because is your alarm line, but when the T1 goes down they take it very serious and jump to repair it. I have seen customers with T1's go down and be repaired within the hour. The other advantage is for non monitored alarm systems (ones that dont contact the monitoring company through the phone line every hour)I have seen occasions where the customer had a POTS line go down on this type of system and didn't find out about it until there was a problem and the system was unable to dial out (sometimes the POTS line can lose dialtone but still have talk battery on the line so the alarm panel cant tell the line is bad and wont set off an audible alarm)the line may have been down for weeks,but believe me the second the T! goes down everyone in the office is going to know.
Hope this helps!

 

[donb01]

I work in the medical industry (in WI) and as far as I am aware, using a T1 line here (even if you have equipment that is designed to communicate on one without requiring a channel bank) WILL NOT meet the requirements of the Life Safety Code (at least for fire protection). The primary reason for that is the Life Safety Code requires 2 SEPARATE lines, a primary and secondary, for external communication. If either one fails the other is used to send the trouble out to the monitoring point (there is no contingency for if both fail other than the audible warning on the system panel in the building).

Theoretically you could use 2 SEPARATE T1 lines for the purpose, but that would be kinda financially stupid, and would still require substantial battery backup to keep the CSU/DSU running, etc.

As already stated above, you also want to make sure that the CO/1MB lines used for the fire/security application are not provided on concentrators, pairgains, etc., because the voltage on the lines is not stable and you will get nuisance troubles on the lines (comm failures) that are VERY difficult to diagnose.

I have replaced non- life safety trunk lines/CO lines with ISDN PRI for the cost savings also stated above, but you also need to consider that you need to keep a few copper CO lines around even then for the inevitable situation when the T1 line goes down....

 

[SYQUEST]

Your points are all well taken, but the "Life Safety Code" has NO control over how the LECs provision the service ordered, and in a lot of areas now, especially with all the remote DLC terminals, you WON"T get any copper to the CO! (Verizon/Bell Atlantic)

Also, in the case where the DS1 terminates on customer equipment or Channel Banks, etc. most service providers I know do not "roll" anything for a DS1 alarm unless the customer reports it as down. I know there are exceptions.

So you just need to do the job right and hope for the best.

....JIM....