atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's 2 Wire T1 vs. 4 Wire T1

I know what you mean, Trace. I asked the same question the first time that I saw it. It technically does provide separate transmit and receive paths, just at different frequencies over the same pair. Very similar to ADSL, where you can have voice and DSL riding on the same pair.

As far as paying, well they technically are providing you with a four-wire circuit. How they emulate it is up to them. I often say the same thing when a carrier puts in a channel bank for 24 POTS lines, but still charges for the POTS lines as if they were all on separate pairs. That's where the telcos make the real money, by reducing transport costs.

HDSL2 technology (2-wire) (whether it be Adtran or ADC the most common equipment manufactures) is just as reliable as a 4-wire T1 delivery method. As a matter of fact it’s MORE reliable than say transmitting and receiving DSX format over copper spans as was done years ago.

This is not like ADSL what so ever in that the bandwidth is synched and locked at 1.544 Mbps transmit and receive. You WILL NOT have bandwidth capacity issues with it. If the T1 can not run at 1.544 Mbps it has lost synch and it’s down.

A T1 is still a 4-wire service as far as billing and tariff goes as well… There’s a 4-wire interface on the customer side of the H2TU-R and it DOES operate “full-duplex” over the one pair of wires.

Works like a champ!

I see a lot of them here as well...HDSL and HDSL2.
Your physical connection is still the same though.

That answers a couple of my other questions Bryan. Thanks for the reply.

When AT&T first started supplying the 2-wire circuits to Birch in this market, Birch had so many problems with them that they started refusing any loop that wasn't a 4-wire in Dallas. That was five years ago however. It sounds like they have really gotten the technology cleaned up.

Well I suppose since it actually is full duplex and has been signed off on by the Tech Talk T1 Braintrust I'll stop whining about it.

Thanks for sharing all the knowledge guys.

:toast:

I like your idea of the large simultanious (bi-directional) transfer across the HDSL.

I agree that HDSL at minimum, is equally as reliable as a regular 4-wire T1. Now that I think of it, Bryan brings up a great point that HDSLs are either UP, or their DOWN.

I'd like to share a quick follow-on point about ADSL Service: Here locally, ADSL is a DSL service that is assigned to an ordinary POTS line. The POTS line is assigned no differently in the switch, with exception that the pair passes thru an ADSL shelf prior to leaving the CO.

Been waiting for you Mike. My lead tech was waiting for a switch operator to chime in before he was ready to concede.

At least from a maintenance perspective (and it's strictly my personal opinion), I think that AT&T's switching your service over to an HDSL circuit could turn out to be a plus. Was there any history of re-occuring issues with the original T1? Now, as far as the cost between the T1 and HDSL? That's definately worth looking into. It does sound like what Ed mentioned with the 24 POTS / Channelized T1 / Channel bank example. I wonder if anyone else has experienced this particular type of "automatic" service switch by AT&T. This could be a new trend..I wonder if Anthony is seing this up in his area.. or if this is standard for AT&T..I wish I knew.

Birch Telecom; I remember (without knowing the details) that Birch went thru quite a tough struggle a couple years ago. Especially with their operating right there in the back yards of SBC, BellSouth, AT&T, I know that Birch has emerged from some very, very, tough times.

Sorry for my recent lag time with responses. This is of those time periods where I have to really struggle to get here. (It's not so much as time, as it is physical access.) I'll have to join the nightowls here until my day schedule "fixes itself".. :thumb:

Darn, you caught me ramblin..

From a carrier point of view, I don't think you have anything to worry about. I work for a large CLEC and we have these installed all over our 15 state footprint. We have VERY few issues that I would say are specifically related to the circuit being a 2wire.

I wouldn't get wrapped around the axle about it being called a 2-wire circuit because whether it's a 2wire or a 4wire, 99% of the time, it will still be an HDSL circuit. IM me on yahoo if you have more questions, and I would be happy to go into more detail or answer more questiong that you have.

Thanks Mike (Megatel). We have a lot of respect for Mike (5Etek-mike) and he speaks very highly of you. Welcome to the board.



Man, it's getting so you can't tell all the Mikes around here without a program.