E1/T1 Trunk Introduction

E1/T1 is known as Primary Rate Interface (PRI), is an Integrated Services Digital Network (ISDN) access method, which enables traditional phone lines to carry voice, data and video traffic, among others.

Note: Yeastar S100 and S300 supports PRI E1/T1/J1 trunk. To extend E1/T1/J1 trunk, you need to install EX30 expansion board on S100/S300. One EX30 expansion board provides 1 E1/T1/J1 port.

The PRI consists of B channels at 64 kbit/s each and D channel at 64 kbit/s each. The B channels are used for voice or user data, and the D channel is used for any combination of data, control/signalling, and X.25 packet networking.

According to the number of B-channels and D-channels, there are three types of PRI interface: E1, T1 and J1.

Table 1. The difference between E1, T1, and J1
PRIs Type Description

Contains 30 B-channels and one D-channel and used in Europe, China and most of the Asia countries.

T1 Contains 23 B-channels and one D-channel and used in the USA, Canada and Hong Kong.
J1 It is almost the same as T1 but used in Japan with some slight modifications, this is the Japanese standard for PRI.