atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's T1 Max distance

What is the farthest you can run a t1 out of the smart jack on house c3 cable before a repeater of some sort is needed?

About as far as I've gone is around 300 feet. this link says 655 feet with 22 gauge.

Standard Line Build Outs for T-1s on the T-3 Mux's were:

1-133'
133-266'
266-399'
399-533'
533-655'

After 655' you needed repeaters. There were CO repeaters (130 Volt) that would push a T-1 for "A Country Mile" (about 6,000'). There were also "Short Haul" Repeaters designed for inside buildings that ran on 48V. Depending where you put them in the run (the middle or one of the ends) you could get 2,000-4,000' on a run.


Sam

I have read that the max 655 foot line build out is to the cross connect patch panel or frame within a building and then you are allowed an 85 foot cross connect. With that in mind the line build out from a smart jack to a cross connect patch panel (DSX-1) would be 655 feet, then the line build out from the the CSU/DSU to the cross connect patch would also be 655 feet. Add in the maximum of 85 foot of cross connect wire to connect the smart jack to the CSU/DSU and you get a max distance of 1395 feet.

I wouldn't use CAT3 for a PRI-- That really is made for DDS. You should use CAT5.

The 655 Foot rule is for the interconnection of line interface unit (LIU) DS1 modules when terminating at a DSX-1 cross-connect frame. Repeated T1 spans are two metallic wire twisted pairs with regeneration typically at 36dB insertion loss points based on 772KHz NYQUIST (one half the T1 line rate), and Roughly at 6000 Feet, or depending on AWG used.

Cat 3 or CAT 6 twisted pair can be used, as long as transmit & receive are run in seperate cables to reduce the incident of cross-talk errors when T1 signal losses are 15dB or greater between TX & RX.

All Verizon T1 NIU's, including all HDSL HTU-R remote units provide T1 signal regeneration on the input side of the unit.

The original Vz RFP requirement was that the NIU/HDSL Remote must recover a DS1 signal down -22.5 dBdsx. Most units will recover down to at least a -30.0 dBdsx value.

So extending a DS1 out to about 3 or 4KFT using 24AWG shold work. A Head to Head Line loss & BER test measurements will validate the T1 span design.

The T1 level output from the NIU/HTU-R however may vary based on region (Formet BA/GTE), and device type and will influence how long a T1 extension can be built before additional regeneration is required.

Vz's deployed Westell 6170 series T1 NIU's (Smartjacks) up until January 2007 were shipped from the factory with a 7.5 LBO option ON by default. The Pairgain (Now ADC) HDSL2 remote had the same 7.5 LBO output default option.

I can't recall if the Adtran HDSL-2/4 incorporated the same (I was not on that RFP when it took place in 2001/2002).

All Westell T1 NIU's deliverd since about January '07 now have the 7.5dB option turned OFF, but available if the CPE side installation requires it. The same 0 LBO output rule change applied to HDSL equipment.

The above default LBO change was my last engineering recomendation at Vz, and a reversal to a recomendion made during my NYNEX days, and implemented in '98 when BA rolled into town.

Field OPS

hey field ops-you're right. I have a cust. pushing 3000 ft from demarc smartjk to a carrier access device channel bank-I have a new clec that says their iax (cisco) has to be within 333 ft of(same) smartjk-Don't you think due to the standards you mentioned, all outputs would be to that spec, not an ethernet spec and if the smart jk can push it any complying equip would recieve it. I keep telling the clec engineers they need to order it right from the telco, which I don't know what that term would be and I worked for Vz for 30. In my day not too long ago there was dip switchs to adjust the output. Are they allowed to crank it up? Do you order it as +7.5. Full power Scotty....

To further my previous question, A T1 to the FCC is the same if its data, voice channels, PRI or combo, and all equipment for use on this spec is about whether it gets the ride in as DB's, and the smartjks have an automatic recovery back to 0 from -22 down and they can be optioned for 7.5 more? Damnit Jim, I am just a tech, not an engineer.Help

ndt4u

There are two basic DS1 circuit terminations that you remain cognizant of. The most typical DS1 termination is found at end user customer locations where the LEC (Service Provider) provides a T1 line termination at a Network Interface (NI).

Typically a tariffed offering for just about all hi-cap T1 services. Regardless of frame format (SF/ESF), or line code (AMI/B8ZS Option), and typically cited in PSC filings as being in compliance with ANSI T1.403.

The ANSI-T1.403 compliant interface is essentially the old fashion T1 span that at one time terminated in a LEC provided CSU. The CSU was the last line repeater in the design of legacy T1 span repeateed metallic 4W lines.

The CSU, just like it s counterpart in the Central Office , the Span Powering T1 Office Repeater (ORB), provided an interface between the outside metallic 4W plant, and terminal equipment.

Both the T1 ORB and T1 CSU provide signal regeneration in the receive direction (From the OSP cable), provide line build out to/from the OSP cable, and more critically, provide DS1 pre-equalization towards the DSX-1.

Equipment designed to operate at the DSX-1 typically will not regenerate a DS1 signal. The purpose of the DSX-1 is to engineer all DS1 equipment to reach the DSX at a specified signal value of 6 volts Peak-to-Peak (6v P-P) 3 volts base to peak signal, with an allowable deviation of =/- 1.2v from the 6v value.

Equipment designed for a standard DSX-1 interface is engineered to operate no more than 655 feet from the DSX-1 when using 22AWG shielded ABAM cable. As the cable gauge gets smaller, the distance between the DSX-1 and equipment gets shorter.

The problem that I have seen is where a channel bank equipped with a LIU module, as opposed to a CSU module, is connected to the t1.403 compliant T1 line, and where the T1 NIU (Smartjack), and CPE are not collocated. Since the LIU module is expected to be within 655 feet of the DSX-1, the signal coming in from the T1 NIU may be too low in signal amplitude to be detected by the channel bank's LIU. This assumes that 22AWG cable is used on the CPE I/W side.

Going the other way to the network is no problem, since the T1 NIU will regenerate a DS1 signal down to 30dBdsx.

Assuming that the you local LEC is using T1 NIU's that output a 0.0dBdsx, and if you are using 24AWG CAT5/6 cable, the maximum distance between the T1 NIU and a channel bank equipped with a LIU module will be about 1/3 less in distance than if you had used 22AWG cable. 24AWG, about 420 feet max. If the LIU can recover a DS1 signal lower than -3.5dB , then you may be able to go out farther on cable.

When IXc Carriers & CLEC's order a T1 access line from an ILEC, the ICX/CLEC use Network Channel (NC) Codes. The NC code defines the DS1 channel type. SF/ESF, AMI/B8ZS. Along with the NC code there is something known as a Network Channel Interface (NCI) code. This also specifies frame format & line code at each T1 interface.

End user customer locations that terminate in ANSI T1.403 compliant interfaces use a 04DU9 NCI codes (Requires a T1 CSU). DS1 interfaces that terminate in DSX-1 interfaces are assigned 04DS9 NCI codes (No T1 CSU required).

Equipment designed to connect to a 04DU9 interface (T1.403), does not mate very well with equipment designed to interface 04DS9 interfaces.

Sorry about the very long winded reply. But if you can remember the differences between equipment based on interface requirements, you will be able to quickly identify a design flaw that may surface under the right conditions.

Experience has shown that PBX trunk card line interfaces units are also not immune from the same design limitations as the channel bank you make mention of. Hence the requirement for an external T1 CSU, or CSU module, to regenerate the LEC DS1 receive signal towards the CSR terminal equipment.

Field Ops

PS: CLECS are notorious for using channel bank (For example: Adtran Total-Reach 750) equipment that does not regenerate the LEC receive signal when equipped with a plain old vanilla DSX-1 LIU module. as for DS1 (T1's) in general, payload is payload. Regardless of what type of information a T1 carries, voice or Data (To a DS1 line payload it all data) the rules for T1 design remain the same.

Filed Ops