How to connect two Asterisk PBXs using a T1 Trunk
This webpage will discuss how to connect two Asterisk PBXs together
using a T1 trunk. The T1 trunk will be configured as an ISDN PRI rate
trunk.
Brief Talk about T1 trunking
A T1 trunk consists of 24 channels of 64 kbps of data operating at 1.544
Mbps. It is a serial connection over UTP and provides full duplex
communications. The connectors are RJ45 connectors the same as Ethernet.
The pinout is different and a crossover cable pinout can be found
here. The assumption at this point is that your
T1 card has been tested and appears to be functioning properly.
The data channels can be configured to pretty much anything you want it
to be. You can combine the channels to create a channel with 384 kbps
bandwidth or you can use only part of the 24 channels. If you use only
part of the T1 available bandwidth, it is called fractional T1.
The control of the T1 channels can be in-band or out of band. If it is
in-band, bits are robbed from the 64 kbps channel for signaling. The
result is 56 kbps for data per channel but you have 24 channels
available for data. This robbed bit signaling is not used too much
anymore due to the lower bandwidth per channel.
Out of band signaling uses one complete channel for control. This means
that 23 channels of 64 kbps are available for data and the 24th is used
for signaling. Any channel can be used for control, it doesn't have to
be the 24th.
