T1 and E1 Lines

E1 and T1 Lines

E1 and T1 standards are basically introduced for voice communication. Both are using TDM for frame formation. In this video, we will discuss the digital transmission advantages and disadvantages. Basic concept about Modulation, Multiplexing, and PCM is already discussed.

Digital Transmission

  • Transmission of digital signals from one point to another point or from one system to another system.
  • The signal source may be analog. At the transmitter side, it is converted to digital and at receiver side again into analog.
  • A physical media is used between endpoints, as it could not travel in free space.

Why digital transmission

  • Less susceptible to interference caused by noise due to the discrete level.
  • Easy to detect errors due to the discrete level.
  • Easy to encrypt(Higher security).
  • Cheaper to implement due to advancement in digital electronics.
  • Digital signal is better suitable for Multiplexing
  • It is simpler to store a digital signal.


  • Require precise time synchronization.
  • Require more bandwidth than simply transmitting the analog signal.
  • Additional encoding and decoding process is required for analog signal.
  • Not compatible with the older transmission system.


  • Modulation is the process of changing the properties of one signal(carrier) with respect to another signal (Information).



E1 is European standard and its basic data rate is 2.048Mbps.It has 30 voice channel and 02 control channel.


T1 is American standard and its basic data rate is 1.544Mbps.It has 24 voice channel and 01 framing bit.

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