Why do I need a DSU/CSU with a DS1 Card? 1

[CCBtx]

I need some help.

I have a number of DS1 Cards (9 to be exact)... 3 in each system.

I have been led to believe that I need a DSU/CSU device between my Magix(s) and the Telco. I have also been led to believe that a 100 DCD Card alleviates the need for a DSU/CSU... because it is built in.

Ok. Fair enough.

However, my T1s (configured as PRIs) coming from the Telco plug straight in to my DS1 card with no extra equipment needed. They work perfectly.

What am I missing here. What is a DSU/CSU and why do I need it if all works fine?

My Avaya service guy is absolutley insistant that I use one(nine actually).

Thanks,

CCB

 

[SYQUEST]

Only because the FCC originally required one. I only provide them when I have cable runs between the NIU and the switch when the length exceeds about 100'. The DSU is only a function of an access router or data device, not part of the DS1 card if it has no data functions. DS1 transmission has equalization and loss requirements tied to cable lengths. To maintain the proper pulse shape and line build out the CSU or DS1 repeater is the only device that can do it. The CSU also provides loopback functions for testing and troubleshooting, along with test jacks for monitoring, etc. at the DS1 level. Some even provide framing and line coding options.

Now the 100DCD does have one built in, but they do not have a stellar performance history. So they can be disabled if they cause problems.

....JIM....

 

[CCBtx]

Wow. I am going to quote you!!!!!

Thanks a lot. My cable run is only 3 feet from the DMark.

...so I suppose I do not need it.

...but I really needed that information.

Thanks again.

CCB

 

[dagwoodsystems]

I'm pretty sure that the FCC still requires that T1s (among many other digital services) terminate at the customer prem with a CSU; I'm very sure that most telcos require one.

Signal regeneration is only one of the CSU's functions. Without one, there's really no way to perform loopback testing from the carrier side. A "metallic" loopback isn't enough; it requires someone to be present on the CPE end and doesn't test through the equipment interface. CSUs are also responsible for sending AIS toward the carrier, which is also useful for troubleshooting (just because channels are down doesn't mean the CPE is necessarily down).

But it isn't all about the carrier. CSUs have buffers and other electronics to iron out timing glitches such as bipolar violations and clock slips. They are also responsible for 1's density (pulse density) and keep-alive signals. Despite your experience so far, you WANT the circuit stability that a CSU-less termination cannot ensure.

However, I understand your frustration and alarm. Yes, your T1 can technically operate without one. You can also technically drive without a seatbelt with a beer in your free hand...doesn't make it right.

Consider using 100DCD cards in your future installations. The increased cost over the 100DS1 is still considerably less than a bottom-of-the-bucket external CSU.

Tim Alberstein

http://www.dagwoodsystems.com

 

[CCBtx]

Excellent advice.

I think I will take it.

CCB