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.

 

[FIREANDSECURITY]

Thanks all for the information. Based on your input I forwarded this request for technical interpretation to NFPA:

What I have been able to learn about the T1 is summarized below, and any or all of these operation characteristics may apply. The equipment information is based on information provided by others believed to be in the telecom field.
• A T1 brings 2-pair of wire to the premises.
• Pair 1 is a digital signal of combined voice/data transmissions to the location with the T1.
• Pair 1 goes to a live T-1/PRI interface at the service location using the phone/data lines.
• Pair 1 goes the from the T-1/PRI interface to a CSU/DSUs interface.
• Pair 1 then goes to a PBX or channel bank in order to break out 24 analog channels or a channel back that breaks out analog trunks and pass lines data.
• The second pair is power provided to power up a smart jack that allows testing of the CSU/DSUs.
• Dialtone is generated at the premises and not the central office.

Additional operating characteristics:
• Only 1-pair of wires will provide up to 24 voice lines for this facility.
• All phone lines are being generated by the same piece of T1 equipment.
• The T1 equipment is not listed as a fire alarm signal transmission/communication device that I am aware of.
• There is not a single loop start telephone circuit from the central office.
• The equipment may not allow the DACT to automatically go off hook to disconnect an incoming or outgoing call.
• Nothing has been provided that indicates that the loss of the Pair-1 in line will result in a trouble signal being transmitted to the fire alarm control
• Modifications to the T1 equipment may be made that could prevent fire alarm signal transmission at any time.
• Programming changes may be made to the T1 equipment that could prevent transmission of fire alarm signals.
• 120vac failure may not be transmitted to the fire control by the (T1) equipment.
• Low battery may not be transmitted to the fire control by the (T1) equipment.
• There is nothing to indicate that dial tone voltage will be discontinued if Pair-1 data line service is lost from the signal generation office.

Question 1. Will the T1 be acceptable for use as a communications method for supervising station fire stations using a DACT(digital alarm communicator technology) as indicated in 8.6.3.2 NFPA 2007?

Question 2. Will the T1 be acceptable for use as a communications method for supervising station fire stations using Other Transmission Technologies as indicated in 8.6.4 NFPA 2007?

NFPA answered the T1 "does not comply with the requirements of Chapter 8.6.3.2" and using a DACT is not permitted under "other technologies" in 8.6.4.

So using a T1 for transmitting fire alarm signals is not permissable. Anyone wanting to see a copy of let me know and I will attach a copy.

 

[SYQUEST]

Several of your bullet points are in error:

The DS1 transmission uses 2 pairs, a transmit pair and a receive pair. Where the service is loop powered, it uses a phantom powering method across both pairs. This powering is for the Telco equipment only, NOT customer equipment.

Any commercial power requirements are to be provided by the customer for their equipment. If Telco places any equipment (channel bank, multiplexer) they usually have some sort of battery backup supply for their hardware.

There are several ways DS1 service can be provisioned:
1. On 2 copper pairs from the CO with DS1 repeaters.
2. On 1 or 2 pairs using HDSL/HDSL2 transmission methods and equipment with or without doublers.
3. On a fiber transmission system utilizing a high level multiplexer to DS1 format.
4. From a DLC or remote terminal or Fiber multiplexer to serving cable.

All of these arrangements terminate on a Network Interface Unit (NIU) for the customers connection point which is a 2 pair connecting arrangement (jack or terminal block or DSX-1).

If you loose one pair, you are out of service.
Dialtone comes from the Central Office switch, not the channel bank.
A Channel Bank or similar Multiplexer type hardware "breakes out" the DS1 channels for services provisioned. In the case of a pots line, the equipment used will determine what kind of line conditions one would experience for a given state or mode of the line. Most channel Banks have alarm indicating capabilities, contact closure, etc.

Hopefully this will clarify some of the inaccuracies in your post.

I think it would be most beneficial if you would post the NFPA 8.6.3.2 and 8.6.4 sections on the forum for all to see. That way we can get a better idea of what the NFPA's ideas and intentions are on this subject.

....JIM....

 

[FIREANDSECURITY]

Thanks for the addl info. I let this post sit for a month for comment before I moved to the next step. I believed I had represented the T1 issue accurately based on what I could google and the comments on this forum. Now looks like I may be close but not entirely accurate. Maybe the manufacturers may need to seek NFPA and UL listing ....I guess????? One thing im sure of is that im not in the tele business, and from my perspective I have asked guys in the tele business and it appears that they can not agree on what it is, or how it works either.
I will forward a request to post the NFPA references on this website. I hesitate to post without doing so as you should be aware of.
Louis

 

[SNSSMIS]

I love T1