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Framed vs Unframed Circuit

Level 1
Level 1

What is the diffrence between farmed and unframed circuit and also between channelized and unchannelized circuit.

3 Replies 3

Level 1
Level 1

Hi Kuldeep,

If I still correctly remember,

In a framed circuit there is a dedicated channel for signalling whereas in unframed circuit the data channel shares the signalling part for the circuit. In unframed circuit every 6th channel shares some part for signalling and the remaining part is for data.


Level 1
Level 1

An unchannelised circuit is a bit pipe transfering bits at a certain rate such as 2048kbps. The way of coding the bits on the line is determined by specifications such as G.703. For me unchannelized and unframed are synonyms.

Channelised (=framed) circuits adds structure to the bit pipe by introducing channels grouped into frames to form a TDM link (such as specified in G.704)


Basically, a channelized (structured) circuit is a circuit that can be subdivided into different channels. While an unchannelized (unstructured) circuit is a circuit that utilized the maximum bandwidth of that given circuit and is not or could not be subdivided into smaller channels. Take an E1 as an example. The unstructured E1 is used as a whole E1 with 2048kbps of bandwidth. It is provisioned as a single E1 link with such bandwidth as your circuit. These are commonly used for high bandwidth leased lines. As for the structured (channelized) E1. This can be divided into 31 64kbps channels called timeslots unique to each other. These individual channels can be subdivided using a multiplexer. Meaning, your E1 goes into a multiplexer and produces 31 64Kbps circuits. Of course, it is up to you on how you would divide your circuits as long as there is enough bandwidth. For example, a 2048kbps circuit could be subdivided into 4 x 512kbs circuits. These depends on the equipment that you are using. Same concept applies to other transmission structured/channelized links such as a T1 = 24x56Kbps or the STM1 (155MBps) = 3 DS3/T3 (45MBps) = 63xE1s (2.048MBps).

Hope this helps! Ü


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