Transmission Lines and their protocols.

[mani_sohail]

plz tell me the transmission protocols.why we use E1 mode instead of T1 mode.

 

[flatulent]

These came from the early days of digital telephone transmissions. T1 originated in the US and E1 in Europe.

 

[mani_sohail]

What is the difference between T1 and E1.
How we convert T1 into E1 and vice versa.

 

[flatulent]

These terms are not precisely defined in engineering conversations.

Originally, they were base band voltage waveforms with specific protocols that were used on cables that originally carried FDM analog telephone signals. They were optimized to carry the same number of telephone signals, only digitized.

Today, they can also mean a portion of a digital stream at the same bit rate but is sent over microwave or fiber optic links. These bits can be of ordinary data and not telephone conversations.

T1 is about 1.544 Mb/s and E1 is about 2.048 Mb/s so you cannot go from E1 to T1 if the E1 is running at full capacity.

 

[papyaki]

Hi,

E1 clock rate = 2048kbit/s
T1 clock rate = 1544kbit/s

E1 carry 32 timeslots (0-31)
T1 carry 24 timeslots (1-24)

1 Timeslot = 1 byte = 1 digitalized voice channel or 1 digital data channel.

E1 framing alignement is made through timeslot 0
T1 framing alignement is made through an additionnal bit, F bit.

See ITU-T G.703 recommandation for electrical caracteristics.
See ITU-T G.704 recommandation for frame structure.
See ITU-T G.706 recommandation for framing alignement and CRC procedure.

Conversion from E1 to T1 can be such a way:

E1 Network connection -> E1 electrical interface -> E1 framing synchronization and clock extraction -> Timeslot extraction -> T1 framing generation -> T1 electrical interface -> T1 network connection.

Only 24 timeslots of a full E1 link can be copied to a T1 link.

Regards