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E1

G.703

https://www.itu.int/rec/T-REC-G.703/en

32 * 64K Time Slots free running

G.704

https://www.itu.int/rec/T-REC-G.704/en

32 * 64K Time Slots, 0,15 are D channels and 1-14,16-31 are B channels in PRI

An E1 circuit provide a transmission speed of 2.04b Mb/s (2m). The 2Mb is made up of a frame containing 64 kb/s timeslots.

The timeslots can be allocated as follows:

TS0: Framing.
TS1 -15: Voice/Data traffic
TS16: Signalling
TS 17 -TS32: Voice Data Traffic

The actual use of the timeslots can be configured depending upon the use of the E1. The example above is taken from a traditional telecoms E1 circuit.

For datacomms the following might be used:

TS0: Framing
TS1 -TS32: Data traffic

!
!
controller E1 0/0/0
clock source internal
channel-group 0 timeslots 1-31
!
!

or

TS0 -TS32: Data traffic

The first of these (TS1-TS32 for Data) is an example of Channelized E1, and is used where the framing is required. Often referred to as G.704 (the ITU standard). Channelized E1 allows any of the 32 timeslots to be identified and extracted.

The second is Unchannelized, and used where no framing is required (G.703) and is used where the full bandwidth (2 Mb/s) is required, and timeslot extraction is not required.