INTRODUCTION
4
1 . 8. 3 E1 Path Overhead
8 bits are used for path overhead and provide framing, alarm information, error detection and
management. The bits of TS0 are used alternatively by the FAS and NFAS frames as
follows:
Figure 1.2 E1 Path overhead
1. 9 DTE Nx64K Payload
The DC3X00 permits the 2.048Mbits/s E1 LINE port to operate with multiple channels of
Nx64Kbit/s where N may vary between 1 and 31. There are restrictions placed upon the
utilisation of bandwidth:
Timeslots used must form a contiguous block
The total number of timeslots allocated must be less than or equal to 31 (or 30 if Timeslot 16
is by-passed).
If Timeslot 16 by-pass is
ENABLED
by setting the bit-switch labelled
BYP16
to
ON,
Timeslot 16 is by-passed in allocating channels sequentially to timeslots; i.e. you could then
select Timeslots ….14,15,17,18…….
Bit No
Function
FAS Frame
1
CRC bit
2 to 8
Frame alignment signal (FAS) 0011011
NFAS Frame
1
International bit : contains CRC multi-
frame alignment signal and remote block
error (REBE) information
2
NFAS bit
3
Remote alarm indication (RAI)
4 to 8
National bits
