[Asterisk-Users] Whitenoise on TDM400p

[Mark Spencer]

> Could there be problems with noise on the line if you use a single CAT5
> cable to carry all 4 phone lines? That is what I have done (just attach 4
> rj-11 on each end) and while 2 of the lines seem fine, one seems to have a
> fairly loud 'buzzing' sound...
>
> Is that 'white noise' or is buzzing something different? Would/Should I use
> 4 separate cables, or do I just need to redo some of the wiring to solve the
> problem?

The noise seems to be on the power supply line itself.  We had an FAE from
Silicon Labs come in and actually analyze this on one of the two machines
we know of that have the problem, and we were able to see with an
oscilloscope noise at about a 400mV amplitude (so 800mV peak to peak) on
both the 12V and 5V at about 125 Mhz.  Although the frequency seemed
awfully high to cause this sort of problem, the FAE was quite confident it
would cause the results we're seeing.

We are currently working on trying to evaluate solutions for revising the
board to be able to elimnate the noise from those systems by adding some
additional bypass caps and inductors.

Mark