On Fri, Feb 27, 2009 at 7:49 PM, Jared Smith <jsm...@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? >From what you say an LBO setting of 5 would boost the signal level, which could be "hot". Is there any chance this would cause the card to fail after a while? It appears this site just had 4 port Digium card fail today. > Also, I am trying to cross connect with another Asterisk system with > > the normal LBO setting (i.e. span=1,1,0,esf,b8zs) but as of yet the > > systems aren't seeing each other at all. Could the side with the high > > LBO be confusing the other side somehow? > > Shouldn't be... you did use a T1-crossover cable to cross-connect the > two Asterisk boxes, right? I've got a little T1 cross-connect diagram > at http://www.asteriskdocs.org/cables/ if you need a reference. > Yes, it's a T1 cross over and this problem was resolved after plugging into a working Digium card on the other end. Brandon B.
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