[Asterisk-doc] Connecting to a PRI

[Stephen R. Darragh]

Final point - it's E1 and T1, not E-1 and T-1.  Unless the dash is some 
typographic mark for you.  :)

Gene Naden wrote:
> Thansks to all for your feedback. I have incorporated the following
> suggestions and corrections into this revised doc. Again, further criticism
> is welcome, it has been very helpful so far.
> 
> 1. There is a discussion of E-1. It only lacks an example of the zaptel.conf
> file. The number of channels is 32
> 2. ISDN PRI is a type of signaling used with E-1 and T-1. PRI is spelled
> out: "Primary Rate Interface."
> 3. "D" channels are "delta", not "data"
> 4. Correct spelling of "confiuration"
> 5. No longer says you cannot have PCI cards in a rack-mounted server
> 6. No longer says the cable is RJ45
> 7.  Zapata channels are one-indexed: Zap/1, Zap/2, etc.
> 
> Gene Naden, MA
> Programmer Analyst
> GlobalTeldata II, LLC
> 4700 N. Ravenswood
> Chicago, IL 60640
> (773) 878-3161 x 223
> 
> 
> ------------------------------------------------------------------------
> 
> T-1, E-1 AND PRI
> In the context of Asterisk, T-1 and E-1 are digital telephony schemes 
> that multiplex a number of voice channels onto one line. E-1 is used 
> mainly in Europe and Asia, while T-1 is used in the United States and
> Canada. In either case, signaling and framing information must be 
> carried, either within the voice channels or in separate, non-voice 
> channels. There are various signallng and framing schemes. 
> 
> One signaling scheme that is used with Asterisk for T-1 connections 
> is ISDN PRI (Integrated Services Digital Network, Primary 
> Rate Interface.) With IDSN PRI, a T-1 connection has 24 channels. 
> In the context of Asterisk, channels 1-23 carry voice and are referred 
> to as "B" (bearer) channels. Channel 24 carries signaling information 
> and is referred to as a "D" (delta) channel.
> 
> ISDN PRI signaling is also used for E-1 connections. Such an E-1
> connection has 32 channels. For Asterisk, channels 1-15 and 17-31 carry 
> voice and are called "B" channels, while channel 16 carries signaling 
> information and is called the "D" channel. Channel zero is used for 
> framing. 
> 
> 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.
> 
> All the Digium cards for connecting to a PRI are PCI cards. The TE405P
> 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 configuration file (zaptel.conf). It shows the 
> configuration for a single T-1 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 option "esf" refers to "extended super frame" and "b8zs" refers 
> to coding "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 unless you 
> specify verbose output ("ztcfg -vv"). When you run ztcfg, 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.
> 
> Digium says 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. Zapata channels are indexed starting at one rather than zero 
> (Zap/1, Zap/2, etc.)
> 
> 
> ------------------------------------------------------------------------
> 
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-- 
Stephen Darragh
Technical Director
Informed Technology
Ph: +61 8 9380 4244  Fax: +61 8 9380 4354