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15 — E1 module operating parameters
15.3
E1 framing format
The E1 framing options determine the framing structure and the timeslot usage of a
2.048 Mb/s E1 link. The framing type cannot be changed or configured if any circuits
are connected.
Two framing options are available: CAS and CCS.
Channel associated signaling
With CAS, timeslot 16 is used for channel associated signaling and is not user
configurable. Timeslot 0 is used for framing. The rest of the timeslots are used for
information.
Common channel signaling
With CCS, timeslot 16 is used for circuit 31, which can be configured as an
additional 64 kb/s data channel (typically for the transport of common channel
signaling messages). Timeslot 0 is used for framing. The rest of the timeslots are
labeled as in CAS. Table 15-2 shows the timeslot-to-circuit relationships.
In Table 15-2, a timeslot is the ITU-T specified channel designation of a primary rate
channel, and a circuit is the node management designation of a primary rate channel.
F stands for framing and S stands for signaling.
Procedure 15-2 To configure E1 framing format
CONFIG — POSITION — <Pp> ↵ — OPTIONS — FRAME_TYPE — CCS/CAS*
where p is 1 or 2
* Default
The FRAME_TYPE softkey does not appear if any circuits are connected.
15.4
Signal earthing (E1 G.703 LIM only)
The signal earthing options configure the earth side of the receive and transmit lines
as earthed or floating.
15-4
Table 15-2 CAS and CCS timeslot-to-circuit relationships
Timeslot
0
1
CAS circuit
F
1
CCS circuit
F
1
2
....
15
16
2
....
15
S
2
....
15
31
2902 MainStreet Technical Practices
17
....
29
30
16
....
28
29
16
....
28
29
90-2906-01
May 2002
31
30
30
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