Specifications

Chapter 1 Introduction Installation and Operation Manual
1-8 Functional Description FCD-E1LC Ver. 1.0
Main Link Interface
The main link interface includes a framer and an LIU (line interface unit). The
characteristics and the main functions of the main link interface are described
below.
Main Link Interface Characteristics
The FCD-E1LC main link meets the applicable requirements of ITU-T Rec. G.703,
G.704, G.706, G.732, G.823 and G.826.
The main link port is terminated in an RJ-45 eight-pin connector that supports
two interfaces: 120Ω balanced line interface and 75Ω unbalanced interface.
Normally, the main link uses the balanced interface; to use the unbalanced
interface, all that is needed is to connect the appropriate RJ-45-to-BNC adapter
cable, CBL-RJ45/2BNC/E1/X (offered by RAD). In this case, the interface is
automatically changed and the user’s equipment can be connected to standard
BNC female connectors at the free end of the adapter cable.
The line code is HDB3. The operating mode of the main link interface, DSU or LTU,
is user-selectable. In the DSU mode, the maximum line attenuation is up to 10 dB;
in the LTU mode, the maximum line attenuation is up to 36 dB, which for typical
cables translates to a range of up to 2 km. This allows the FCD-E1LC to be placed
at a distance of up to 2 km.
The interface supports both G732N framing (2 per multiframe) and G732S
framing (16 frames per multiframe, also called timeslot 16 multiframes), in
accordance with ITU-T Rec. G.704 and G.732. The user can also configure the
main link to use the CRC-4 function in accordance with ITU-T Rec. G.704. The use
of the CRC-4 function, as well as the framing mode, is user-selectable.
FCD-E1LC main link can also be operated in an unframed mode, to generate an
ITU-T Rec. G.703 unframed signal. In this mode, FCD-E1LC accepts a 2048 kbps
data stream through a synchronous data channel (or from the optional sublink)
and converts it to an ITU-T Rec. G.703 unframed signal for transport over the E1
main link.
Framer
The transmit path of the framer generates the E1 frame structure transmitted by the
main link port, in accordance with the selected framing mode. The frame structure is
generated by combining the data retrieved from the prescribed timeslots of the TSER
line with the framing overhead, when the main link-framing mode is G732S or
G732N. The TSER line may also carry inband management data generated by the
management subsystem Unused timeslots are filled with a user-selected idle code.
The receive path of the framer extracts the payload data, the inband
management data stream and demultiplexes the incoming E1 data stream.
The framer also collects performance statistics based on framing errors, bipolar
coding violations and errors detected by the CRC-4 monitoring function. These
statistics can be read by the FCD-E1LC management subsystem.