MDS MX-2100, Installation And Operation Manual

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Chapter 1 General Information MX-2100/2104 Installation and Operation Manual
1-42 Application Considerations
MX-2100 E1/T1 Mux
DCE Timing External Timing
DDS
Network
Master
Clock
KH
S.
1
HS
-2
DTE
XMIT
Clock
RCV
Clock
Channel
in DTE2
Timing
Channel
in DTE2
Timing
(Mode 3)
Figure 1-29. Typical DCE (KML.1–4) Timing Application
Internal Timing (KML.5, KML.6, KML.7, KML.8, and KML.F Modules)
When the internal timing mode is used with a KML.5, KML.6, KML.7, KML.8, or
KML.F module, the source for the internal timing signals is a crystal oscillator
located in the main link module.
The internal timing mode can be used in point-to-point links and in independent
networks. In any link or network, only one MX-2100 unit may operate with
internal timing. All the other units must use loopback timing to ensure
synchronization. In this way, the unit that operates with internal timing is the source
of the master clock and determines timing of the entire network.
Figure 1-30 shows a basic network configuration that uses a KML.5 or KML.6
module in the internal timing mode in conjunction with loopback timing.
I/
O
M
odu
le
s
MX-2100 MX-2100
Internal Timing Loopback Timing
I/
O
M
odu
le
s
~
Figure 1-30. Typical Internal Timing Mode Application
Loopback Timing (KML.5, KML.6, KML.7, KML.8, and KML.F Modules)
With loopback timing, the main link transmit clock is locked to the receive clock,
recovered from the receive data signal. In effect, with loopback timing MX-2100 is
sending back data at the same rate data is being received.
The loopback mode can be used as shown in
Figure 1-30 , however there is an
additional important application for the loopback mode, as shown in Figure 1-31 .
In the configuration of Figure 1-31 , two MX-2100 units communicate through a
G.703 link provided by a digital transmission network, e.g., the national network
or a private carrier network, or by the DDS network. Such networks usually
incorporate very accurate timing source, which are always preferable. Loopback
timing then allows the locking of the transmit timing of both MX-2100 units to the
accurate master clock provided by the network.