• What is E1 and T1?

The PDH (plesiochronous Digital Hierarchy) has 2 primary communication systems as its foundation.

These are, 
T1 system based on 1544kbit/s that is recommended by ANSI &
E1 system based on 2048kbit/s that is recommended by ITU-T.

Common Characteristics :-

1.       Both are having Same Sampling Frequency i.e. 8kHz.

2.       In both (E1 & T1) Number of samples/telephone signal = 8000/sec.

3.       In both (E1 & T1) Length of PCM Frame = 1/8000s = 125µs.

4.       In both (E1 & T1) Number of Bits in each code word = 8.

5.       In both (E1 & T1) Telephone Channel Bit Rate = 8000/s x 8 Bit = 64 kbit/s.

Differing Characteristics :-

1. In E1 Encoding/Decoding is followed by A-Law while in T1 Encoding/Decoding is followed by µ-Law.

2. In E1 - 13 Number of Segments in Characteristics while in T1 - 15Number of Segments in Characteristics.

3. In E1 - 32 Number of Timeslots / PCM Frame while in T1 - 24 Number ofTimeslots / PCM Frame.

4. In E1 - 8 x 32 = 256 number of bits / PCM Frame while in T1 - 8 x 24 + 1* = 193 number of bits / PCM Frame. (* Signifies an additional bit).

5. In E1 - (125µs x 8)/256 = approx 3.9µs is the length of an 8-bit Timeslotwhile in T1 - (125µs x 8)/193 = approx 5.2µs is the length of an 8-bit Timeslot.

6.  In E1 - 8000/s x 256 bits = 2048kbit/s is the Bit Rate of Time-Division Multiplexed Signal while in T1 - 8000/s x 193 bits = 1544kbit/s is the Bit Rate of Time-Division Multiplexed Signal.