[Asterisk-doc] Connecting to a PRI

[Gene Naden]

Julian,
    Thanks for your comments.

----- Original Message ----- 
From: "Julian Lyndon-Smith" <asterisk at dotr.com>
To: "Discussions regarding The Asterisk Documentation Project"
<asterisk-doc at lists.digium.com>
Sent: Thursday, August 11, 2005 3:25 PM
Subject: Re: [Asterisk-doc] Connecting to a PRI


> Comments inline:
>
> Many thanks for taking the time to doc this.
>
> Julian.
>
> Gene Naden wrote:
> > Here is my explanation of the issues involved in connecting to a PRI. I
am
> > open to feedback, corrections, comments. This is a text file with line
> > breaks.
> >
> > Gene Naden, MA
> > Programmer Analyst
> > GlobalTeldata II, LLC
> > 4700 N. Ravenswood
> > Chicago, IL 60640
> > (773) 878-3161 x 223
> >
> >
> > ------------------------------------------------------------------------
> >
> > WHAT IS A PRI?
> >
> > A PRI is a 24-channel connection to a telephone network such as the
Public
> > Switched Telephone Network (PSTN). PRI is a type of ISDN (Integrated
> > Services Digital Network) connection. A PRI can carry 23 voice channels.
> > The 24-th channel is used for signalling. The voice channels are
referred
> > to as B channels and the signalling channel is referred to as the D
channel.
>
> Euro ISDN PRI have 31 channels, 16th used for signalling
>
> >
> > Because a PRI uses a four-wire local loop, d4 or esf framing, and AMI or
B8ZS
> > coding, it may also be referred to at T-1. However, T-1 can be used to
carry
> > either voice or digital data.
>
> or E1 for euroisdn
>
> >
> > You specify the type of framing and coding when you provision the PRI
with the
> > telephone company.
> >
> > CONNECTING TO A PRI
> >
> > To connect to a PRI you use Zapata technology. Zapata is also used for
> > connecting to POTS lines (ordinary, single channel analog phone lines)
and
> > analog phones. You configure Zapata for Asterisk in the file
/etc/zaptel.conf.
> > Therefore this file can have information about both PRI connections and
POTS
> > line connections. See the example below.
> >
> > You do not need a Channel Service Unit/Data Service Unit (CSU/DSU) to
connect
> > your PRI to the Asterisk computer.
> >
> > The Digium cards for PRIs accept RJ45 plugs, the same type of plug used
> > in Category 5 cables.
> >
> > All the Digium cards for connecting to a PRI are PCI cards. Therefore,
you
> > cannot use a 1U rack-mounted server if you are connecting to a PRI. The
TE405P
>
> Um, we are - most 1U servers have riser boards allowing for the card to
> be mounted sideways. Both our TE405p and TE405P are in 1U servers.
>
> > card is an example of a PRI interface card. It has four ports and
therefore
> > can connect to up to four PRIs. Alternatively, one or more ports could
be
> > connected to channel banks for analog phones. However, channel banks are
> > beyond the scope of this discussion.
> >
> > Below is a sample Zapata configuraion file (zaptel.conf). It shows the
> > configuration for a single PRI, two analog phones and two POTS lines.
> >
> > # zaptel.conf
> >
> > loadzone = us
> >
> > #te405p card
> > span=1,1,0,esf,b8zs
> > bchan=1-23
> > dchan=24
> > fxols=1-23
>
> >
> > #tdm400 card
> > fxoks=97-98
> > fxsks=99-100
> >
> > The 23 B channels and the D channel are shown.
> >
> > The line "fxols=1-23" reflects the fact that the connection is to a PRI
> > rather than a channel bank. "ls" refers to "loop start."
> >
> > The way the channel numbering works is that the first 96 channels (one
> > through 96) are for the TE405P card. The fxo and fxs channels, if any,
> > must follow, rather than precede, the PRI channels. In other words,
> > you cannot have fxoks=1-2, fxsks=3-4, bchan=5-27, dchan=28. If you
> > do this you will get an obscure error message.
> >
> > Regarding the line beginning with the word "span", there is one span
> > for each port that is in use. The "span" line has the following format:
> >
> > span=port number, timing, line build out, framing, coding
> >
> > The port number is one because the PRI is connected to the first port on
the
> > card.
> >
> > The timing should be 1 for one of the ports. The line connected to that
> > port provides a timing reference. If other ports are used, the timing
for those
> > ports should be two or zero. Two means this line is a secondary timing
reference
> > and zero means this line is not used as a timing reference.
> >
> > Line build out reflects the length of last leg of the connection and is
set to
> > zero if the length is less than 133 feet. The specific values for line
build
> > out are specified in the sample zaptel.conf that comes with Asterisk.
> >
> > The framing and coding are discussed in "WHAT IS A PRI", above. The
option "esf"
> > refers to "extended super frame" and "b8zs" refers to "Bipolar with 8
Zero
> > Substitution."
> >
> > TROUBLE-SHOOTING
> > When the PRI card was purchased from Digium, Digium has provided free
> > technical support for configuring the card.
> >
> > The lights on the PRI card can be red, amber/green or green. When all is
> > well they are green.
> >
> > If Asterisk aborts when you try to start it, there are several things
you
> > can check:
> >
> > The Linux modules for your Zapata cards have to be loaded in order for
the
> > connections to work. You load the PRI driver, wct4xxp, before you load
the
> > FXS/FXO driver, wctdm.
> >
> > You also have to execute the program ztcfg to get things to work. If all
is
> > well, when you run ztcfg it should not produce any output. When you
> > do this, the lights should change to green, even if Asterisk has not
been
> > started.
> >
> > Loading of the modules may or may not be done automatically by the
system.
> >
> > It is possible to construct a loop-back plug to test your PRI card.
> > You do this using an RJ45 plug, connecting pin one to pin four and pin
> > two to pin five. When the loop-back connector is connected to the card,
the
> > light should turn green. Again, the modules have to be loaded and
possibly
> > ztcfg has to have been run.
> >
> > The B channels listed in zaptel.conf must agree with the channels listed
in
> > /etc/asterisk/zapata.conf, otherwise Asterisk may abort when you try to
> > start it.
> >
> >
> > ------------------------------------------------------------------------
> >
> > _______________________________________________
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> > Asterisk-Doc at lists.digium.com
> > http://lists.digium.com/mailman/listinfo/asterisk-doc
>
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