A DCS has the capability to loop any DS-0, DS-1 or DS-3 signal onto itself or any other signal in the digital crossconnect system's electronic matrix. Whether or not the DCS has a test head (e.g., Hekemian or other) outboard or integrated in the DCS is a choice of the carrier. At the command of a DCS admin person a digital signal can be crossconnected to the test head's test port on the DCS, where it can be remotely tested for continuity, signal impairments or other operating parameters. DDS and/or DS-n signals can be generated by the test head and the circuit's response compared against a "signal mask" stored in the test head. Whether or not the circuit meets the carrier's standards for Bit Error Rate (BER) and other operating parameters can be quickly ascertained. I can't believe that Bell Atlantic does not have this capability within their network. Steven NetEffect Corporation ------Original Message------ From: Travis Pugh <tpugh@shore.net> To: Sean Donelan <sean@donelan.com> Sent: May 16, 2000 8:54:22 PM GMT Subject: Re: Bell Atlantic DACS failure 280 T3s I'm curious about BA DACS. I don't know if this is standard, but they are the only telco who has also told me "we put a loop up on the DACS, but sometimes it doesn't work ... so don't assume that it is a valid test." And I have witnessed that same happening. If you can't create a simple maintenance loop on BA's DACS, their choice of vendors does seem questionable. -travis On 16 May 2000, Sean Donelan wrote:

Bell Atlantic lost another DACS yesterday taking out 280 T3s for 3-1/2

hours

in the northeastern corridor and New York City.

I'm not a transmission person, but what is the problem with DACS? Why do these "highly reliable" systems fail in such catastrophic ways?