[asterisk-users] what is the effect of high LBO settings?

[Brandon B.]

On Fri, Feb 27, 2009 at 7:49 PM, Jared Smith <jsmith at digium.com> wrote:

> On Fri, 2009-02-27 at 14:07 -0700, Brandon B. wrote:
> > As of yet, I am unwilling to change the LBO to 0 to where it probably
> > should be because the system is working and I'm not sure exactly what
> > the LBO does. I'm aware some changes were made to deal with low audio
> > levels.
>
> LBO stands for Line Built Out... it's essentially a measurement of the
> distance between your demarcation point (d-marc/smart jack/NIU) and your
> Asterisk box.  As you can see from a sample system.conf (from DAHDI) or
> zaptel.conf (from Zaptel), it's an integer value from the following
> table:
>
> 0: 0 db (CSU) / 0-133 feet (DSX-1)
> 1: 133-266 feet (DSX-1)
> 2: 266-399 feet (DSX-1)
> 3: 399-533 feet (DSX-1)
> 4: 533-655 feet (DSX-1)
> 5: -7.5db (CSU)
> 6: -15db (CSU)
> 7: -22.5db (CSU)
>
> As I understand it, the LBO is effectively an attenuation value, with a
> higher number meaning less attenuation.  This way, you don't get too hot
> of a signal with a short cable, or two low of a signal on long cable.
>
> Just how far is your Asterisk box from the demarcation point?


This system is connected to a CSU in the same room that provides the
physical T1 line. I've always set the LBO setting at 0 for this  because
I've never had a long line to deal with. Since 0 works for me, I'm going to
assume it's the correct setting with the demarc point (i.e. the Paradyne
CSU) in the same room -- right? It's slightly confusing with settings 5,6,7
labelled CSU and no description as to when to use those levels. Could you
provide any suggestion for when levels 5,6,7 would be appropriate?