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LDK 300 - Noisy digital line

LDK 300 - Noisy digital line

LDK 300 - Noisy digital line


I have an LDK300 system that I have been working on that has a very noisy line on one of the digital ports. (port 15)

The configuration of the system is:

Slot 1 - DTIB12
Slot 2 - DTIB12
Slot 3 - DSIB
Slot 4 - SLIB2
Slot 5 - SLIB2

On port 15 (DTIB12 N2 port 3) when someone calls the phone assigned to port 15, the extension on port 15 can not hear the calling extension due to heavy noise and distortion, however the calling extension can hear phone on port 15 clearly (one way distortion) and the same when the extension assigned to port 15 calls another extension, the person on the other extension can hear clearly, however the person on port 15 can not hear due to the noise and distortion.

I have:
swapped phones on the extension that is connected to port 15 - No change
Swapped DTIB cards over - No change
Moved the cable that is connected to Port 15 at the termination block to a spare port (port 27, port 3 on the DSIB card) and the line is clear both ways
Moved a known good extension from port 3 onto port 15 and the noise is still present on port 15
Swapped the wire pair (green white/white green) with a spare wire pair in the cable that goes from the DTIB12 card to the termination blocks - No change

From this I have eliminated :
The DSIB card,
The wires from the DSIB card to the termination,
The cable from the Termination to the Extension, and
The phone

What is there left that may be causing the interference, could it be the LDK-300 mother board ?? I can't move the DSIB card to another slot due to all the slots being populated (trunk lines, ext)

It is certainly a strange one... The customer was not upset at all with the result as luckily there were spare ports available so I have just moved the extension from Port 15 to one of the spare ports and renumbered the ports to suit, so they have lost no functionality.. But it is very frustrating to not be able to pin down the source of the noise.

Cheers and Beers

RE: LDK 300 - Noisy digital line


I know you've change the cabling but have you tried popping the extension direct on the TJF? This would complete eliminate all wiring. Could be a dodgy connection on the Krone strip for that pair, you could take the wire off and move it to a spare part of the krone strip.


Ok, Press Trans *#..... TRANS/PGM..... the transfer key?.......sigh!

RE: LDK 300 - Noisy digital line

as above . go directly on to the lead from the system it self if you can . to eliminate the krone as well if you can

RE: LDK 300 - Noisy digital line

Hi Bazza,
Another option, if you run out of ideas, is to take a system database backup..
Then default the system and try swopping card positions to eliminate the KSU.. The backplane is not "dumb" and the slot may be the issue... or if you have a maintenance cabinet you could try that too.
You have already done the easy bits...
Regards Steve

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