[asterisk-users] Description of Zaptel/DAHDI E1 alarms

[Jared Smith]

On Mon, 2009-01-19 at 11:10 +0100, Lukas Rypl wrote:
>  I am missing any description of zaptel/DAHDI alarms. The TE200 series
> user manual contains only a description of LEDs states. These alarms
> states are visible in zttool/dahditool or in astersick CLI (zap show
> status) and I wonder what is the real meaning of these alarms for E1
> channel.

I can't speak for all the possible states in the T1/E1 card driver, but
I can state that typically in T1s and E1s you have three different
general alarm states: RED alarms, YELLOW alarms, and BLUE alarms.  (This
is a brief synopsis of the information we cover in the Asterisk Advanced
training class.)

Red alarm
---
Your T1/E1 port will go into red alarm when it maintain synchronization
with the remote switch.  A red alarm typically indicates either a
physical wiring problem, loss of connectivity, or a framing and/or
line-coding mismatch with the remote switch.  When your T1/E1 port loses
sync, it will transmit a yellow alarm to the remote switch to indicate
that it's having a problem receiving signal from the remore switch.
(The easy way to remember this is that the R in red stands for "right
here" and "receive"... indicating that we're having a problem right here
receiving the signal from the remote switch.)

Yellow alarm or RAI (Remote Alarm Indication)
---
Your T1/E1 port will go into yellow alarm when it receives a signal from
the remote switch that the port on that remote switch is in red alarm.
This essentially means that the remote switch is not able to maintain
sync with you, or is not receiving your transmission.  (The easy way to
remember this is that the Y in yellow stands for "yonder"... indicating
that the remote switch (over yonder) isn't able to see what you're
sending.)

Blue alarm or AIS (Alarm Indication Signal)
---
Your T1/E1 port will go into blue alarm when it receives all unframed 1s
on all timeslots from the remote switch.  This is a special signal to
indicate that the remote switch is having problems with it's upstream
connection.  As far as I know, dahdi_tool/zttool and Asterisk don't
correctly indicate a blue alarm (at least I've never seen them indicate
one).  The easy way to remember this is that streams are blue, so a blue
alarm indicates a problem upstream from the switch you're connected to.

I hope the explanation helps.


-- 
Jared Smith
Digium, Inc. | Training Manager