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.