Introduction to T1, E1 & T3


T1 is a special type of fiber optic telephone line and it was developed by AT&T Bell Labs. T1 is the most commonly used digital transmission service in the United States. T1 line is capable of transferring the broadband digital data at very high speed i.e. 1.54 Mbps.  T1 is an expensive solution for data transmission as compared to the regular telephone lines. But the prices are tend to decrease as the demand grows.  Currently T1 is not cost effective for the home users.
A large number of the businesses in USA, Canada and Japan use T1 lines to connect to the internet.  There are different ways to provide T1 transmission such as twisted pair cables, coaxial cable modems, fiber optic systems, common careers and digital radios. 

In large networks T1 signals can be boosted up to 100 miles by using the repeaters.  In telecommunication terminology, T1 is also known as DS1 and T1/DS1 is a method of connecting the digital communication systems with the telecommunication industry and North America.


E1 is a digital data communication system for the European data transmission format.  E1 carries the data signals at the speed of 2 Mbps (Full duplex). E1 and T1 lines can be interconnected with each other for international data transmission. 

E1/T1 are used for the leased lines transmission.  E1 is ideal for the voice traffic and it can carry 32 voice conversions.  An E1 line 32 64-Kbps channels and each channel may be used to send and receive data and voice. 

E1/PR1 (Primary rate interface) supports 30 B channels and one D channel. Primary Rate Interface (PRI) configurations are used to receive multiple analog calls from the dial-in traffic and analog-modems.


A T3 line is 30 times faster than the T1 line and it supports the data transfer rate 44 Mbps.  A T3 line is equivalent to 28 T1 circuits or lines and a T3 is also called a DS3.  T3 is a very high speed data transmission system and it is widely used on the internet. 

A T3 is capable of carrying 672 voice circuits.  T3 connection is mostly used by the ISPs and corporate offices for permanent, high speed and uninterruptible internet access.