[c-nsp] Adtran MX-2800 to PA-MC-T3

[Bill Wichers]

> Hello,
> 	We have a problem that we have exhausted all available resources
> on solving, and we are running into a dead end. We have several T1
> circuits, from various LECs provisioned into a single MX-2800 MUX at our
> location. We then tie that mux into a PA-MC-T3 card on a 7507 in a
> VIP-2-50 to terminate the circuits. The DS-3 cabling is 25 feet in
> length and we have (per Cisco reccomendations) a 6 db attenuator on the
> PA-MC-T3 RX leg. We are running CBIT, w/ the MUX providing timing.
>
> We continue to receive LCVs, C-Bit and P-Bit framing errors, and the DS1
> circuits will occasionally bounce.

Sounds like a clocking issue. All the T1s need to be in sync, and you have
to have one common master clock source coming from somewhere. If you don't
have a master clock, or if the T1s aren't all really synchronous (a real
possibility with multiple carriers), then you might get time slips which
can cause all kinds of wierd framing errors. I have seen similar problems
on circuits that have both ends set to 'slave' for timing.

See if you can get it so that *your mux* provides timing for *everything*
(including ALL the T1 circuits). Some carriers let you be the master for
timing which can make it much easier to setup a system like you have. Then
set all your remote T1 equipment to 'slave'. You might also want to have
the MUX derive timing from the DS3 so that the PA-MC-T3 is the master
timing source for the system.

> I CANNOT find anyplace to buy the ATTEN-KIT-PA online. Our thoughts are
> perhaps we can use progressivly higher attenuation (10,12,16,18 db) but I
> cannot order the kit anywhere. Cisco directs me to Insight, who doesn't
> stock it.
>
> Anyone have any suggestions?

A DS3 just needs a 75 ohm attenuator. Easiest way to get those in a hurry
is to get them from a TV/video supply place (try
http://www.mcmelectronics.com). Get an attenuator of the value you want,
plus one F-to-BNC adapter and a BNC-to-F adapter. You can then use that to
test. If it works, you can get a BNC attenuator (which will be harder to
find and more expensive than the "F" type units) from a professional video
supply place. I'd try working with the timing first though, or just get a
longer DS3 cable made of 735 cabling (735 is the smaller DS3 cable). 735
has more loss and is also easier to handle, so it's generally a better
choice for short runs.

     -Bill


*****************************
Waveform Technology
Systems Engineer