Configurancion de una linea T1 en Dahdi

Configuring a Dahdi T1 Line

This webpage is about configuring a T1 line for Asterisk - it should work equally well for E1 cards. If you haven't at this time, read the pages on this website about Testing Dahdi Hardware. It'll give you an introduction into how the Dahdi cards integrate with Linux and Asterisk - probably too much information!

The script "dahdi_genconf" creates a generic configuration for both the FXS/FXO and E1/T1 Dahdi cards. In most cases, /etc/dahdi/system.conf will have to be manually tweaked to your requirements.

Make sure that your cards are blacklisted as per the instructions at Testing Dahdi Hardware and that the card modules are being loaded at /etc/Dahdi/modules as per the instructions at Dahdi Drivers Once that is verified than you are ready to perform the configuration of the first file: /etc/dahdi/system.conf. At this point you will need to know your service provider's T1 settings or if you are connecting to a channel bank, its T1 configuration.

This webpage is divided into two sections:

1. Configuring the T1 Line Parameters (this page)
2. Configuring the T1 Channel Parameters

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Configuring the T1 Line Parameters

In this example, we will be connecting a TE110p card to an Adtran TSU600 channel bank with a T1 crossover cableusing the following T1 configuration:

• Span 1
• TE110p card provides master clock
• Line build out is for 6 feet
• Framing is for T1 esf
• Coding is standard T1: b8zs
• No yellow alarms

A channel bank provides 24 channels of FXS or FXO ports (any combination of each) from a T1 line. It would be great to use as part of a VOIP gateway from the legacy telephone network to VOIP. Provide VOIP to 24 phone lines (FXO) or connect 24 phones set to the VOIP world, or use it with PiaF to replace an existing key system.

Configuring T1 Line

The following information will configure the T1 interface in /etc/dahdi/system.conf:

span= <span num> ,<timing source>,<line build out (LBO)>,<framing>,<coding>[,yellow]

<span num>

Number of the T1 span. This begins at 1, and goes up one integer at a time. You may NOT have two spans with the same span number. Each telephony card counts as one span.

<timing source>

All T1/E1 spans require a clock signal on their transmit side. The parameter determines who is generating the clock signal for the T1/E1 line. NT means NeTwork, it generates the clock, and TE means Terminal Equipment which receives clock.

0 = Local T1 card provides clock (it is the NT - network termination)
1 = First choice: far end T1 provides clock, local T1 card is TE - terminal equipment
2, 3, ? = Second choice for clock source. This is used if you have multiple T1 cards. If first clock source fails fallover to this one

<line build out (LBO)>

The line build-out (or LBO) is an integer, 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)

<framing>

The framing is one of "d4" or "esf" for T1 or "cas" or "ccs" for E1

Note: "d4" could be referred to as "sf" or "superframe"

<coding>

The coding is one of "ami" or "b8zs" for T1 or "ami" or "hdb3" for E1

E1's may have the additional keyword "crc4" to enable CRC4 checking

[,yellow]

If the keyword "yellow" follows, yellow alarm is transmitted when no channels are open.

Example configurations:

span=1,0,0,esf,b8zs
span=2,1,0,esf,b8zs
span=3,0,0,ccs,hdb3,crc4 

Here's the Adtran Channel Bank Example:

For the example setup of a T1 to a channel bank, our configuration would be:

span=1,0,0,esf,b8zs

• span=1 because it is the first card installed
• 0 because we are going to provide the master clock to the channel bank (1 if we were connecting to a service provider)
• 0 because we are going less than 133 feet from the PiaF server to the channel bank
• esf because Extended Super Frame is the industry standard and we configured the channel bank to use it
• b8zs because bipolar with eight-zero substitution (B8ZS) is the industry standard for T1 lines.

Here's the latest up to date dahdi documents and if you've ever wondered exactly what the T1 alarms (yellow, red, blue, etc..) mean you can find it out at the Dahdi Telephony Interface page.

The next step in communicating with the channel bank is to configure the T1 Channel Parameters

http://www.cadvision.com/blanchas/Asterisk/ConfiguringT1LineDahdi.html