[c-nsp] Line Code Violations on DS3

[Jay Hennigan]

Nick Voth wrote:
>>> Hello folks,
>>>
>>> I need another set of eyes on this. We have a new channelized DS3
>>> plugged in > to a Cisco 7206-VXR with a PA-MC-T3 card. We can't seem to
>> get rid of
>>> the Line Code Violations and P-bit Coding Violations. See what we've done
>>> below this output...
>> Try putting a 12 db attenuator on the transmit portion, then re-try your
>> loopback. We've found that the PA-MC-T3 cards tend to overdrive the DS3 a
>> bit, and the only way that we've been able to get rid of the errors is
>> attenuating the transmit load.
>>
>> Cisco makes a kit for this, but the part number escapes me now.. Try
>> searching for DS3 Attenuator on google..
>>
> 
> Interesting, you're saying to put an attenuator on the transmit portion of
> the card. Some of the Cisco documentation is saying to put it on the receive
> portion. Is there any way using the "show controller" output to tell which
> one has the "hot" signal?

The "cablelength" command can be used to reduce the transmit signal 
(shorter length reduces signal).  Too hot of a transmit level will 
result in far end errors, not near end errors.

In our experience, when attenuators are needed, it has been on the 
receive side of the card.

There are 75 ohm variable/stepped attenuators made for the cable 
television industry that can be useful to dial in the right value, then 
replace with a fixed pad of that value.  One example here:

http://www.kayattenuators.com/manual_step_attenuators.htm

These can occasionally be found at ham radio swapmeets and the like 
pretty cheap.  Make sure you get the 75-ohm version.

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
Impulse Internet Service  -  http://www.impulse.net/
Your local telephone and internet company - 805 884-6323 - WB6RDV