3CX Germany

Askozia Becomes

Try 3CX

What is PRI?

ISDN (Integrated Service Digital Network) is divided into two types of services, BRI (Basic Rate Interface) and PRI (Primary Rate Interface). BRI is mostly used by smaller enterprises, PRI is meant for medium and large enterprises as well as smaller companies who require a high number of parallel calls.

PRI scheme

Both, BRI and PRI are consisting of B and D channels. B-channels carry voice (or data), D-channels carry control and signalling information. BRI consists of two B-channels and one D-channel. PRI is often referred to as T1 (for North America and Japan) and E1 (for Europe and Australia). T1 usually has 23 B-channels and one D-channel, E1 usually 30 B-channels and 2 D-channels. Additionally, there are PRI pairings available consisting of multiple T1/E1 lines, as well as fractional T1/E1 lines with less than 23/30 channels.

Free for up to 1 year! Select preferred deployment:


for Linux on a $200 appliance or as a VM

Get the ISO


for Windows as a VM

Download the setup file

On the cloud

In your Google, Amazon, Azure account

Take the PBX Express