[Asterisk-Users] How to fix a Blue Alarm?? Line Noise?

[Geoff Manning]

We are having line noise issues in our Asterisk to legacy PBX integration.
All SIP calls originating from IP phones sound crystal clear. All calls that
originate from the legacy PBX (Isoetec 228) and route through the Asterisk
and out SIP have a lot of line noise.

I believe I have it pinned down to these Blue Alarm errors that I can see on
the legacy PBX side. zttool shows no alarm but when I view the T1 stats on
the Isoetec I see numerous Blue Alarms.

The TE110P card in the Asterisk server is set as the sync source:

span=1,1,0,d4,ami
e&m=1-24

Our Isoetec tech says that the T1 card in our 228 does not provide timing so
I made the TE110P the sync source.

What are these Blue Alarm errors indicative of? I found some info on the
list but it didn't make much sense to me. Are there additional timing
parameters I can put in zaptel.conf/zapata.conf to fix this?

Thanks!


EVERYTHING BELOW HERE IS INFORMATIVE:

Just incase someone comes along the archive to find solutions for "Line
Noise" I have added this info as I made several adjustments to get the
results of zttest to a 99.99% accuracy.

1) No IRQ sharing
2) Turn *off* hyperthreading
3) Turn off unnecessary settings in BIOS: usb, LPT, serial
4) Turn off "ACPI power management" and the "APIC interrupt controller" in
the kernel.

	acpi=off noapic <-- add these as kernel arguments

These changes brought my average from 99.85 to 99.99