Specifications

MX-2100/2104 Installation and Operation Manual Chapter 1 General Information
Application Considerations 1-41
MX-2100 MX-2100
Modem with
External Timing
E-DCE Timing
(External Source)
DTE Timing
DDS
Network
Master
Clock
Channel
in DTE2
Timing
KHS.1
DTE
XMIT
Clock
RCV
Clock
Modem with
Loopback Timing
Figure 1-28. Typical External DCE Timing Application
• Internal timing. The source for the internal timing signals is a crystal oscillator
located in the KML module. The timing accuracy of this oscillator is ±50 parts
per million (ppm).
The internal timing mode can be used in point-to-point links and in
independent networks. In any system, only one unit may operate with internal
timing. All the other units must use DTE 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.
In the external DCE mode, buffers are used in the main link receive path, but not
in the transmit path. Buffer size is selectable, ±8 or ±256 bits.
DCE Timing (KML.1, KML.2, KML.3 and KML.4 Modules)
With DCE timing, MX-2100 provides both the transmit and receive clock signals to
the equipment to which it is connected. The timing reference source of the
transmit timing signals can be selected as for the external DCE mode. The
connected equipment must then use the DTE timing mode.
The DCE timing mode is useful when the MX-2100 main link is connected to a
channel of a corporate data transmission system (e.g., the main link of one of the
MX-2100 units is connected to a data channel of an E1/T1 multiplexer), and one
or more of the MX-2100 channels are connected to a data network which
provides accurate timing (e.g., to a DDS link, an ISDN line, or another data
network). In this case, the network timing can be distributed through MX-2100 to
the other parts of the system. Figure 1-29 shows a typical connection to a DDS
network through a KHS.1 module; for connection to an ISDN line, replace the
KHS.1 module with a KHS.U module.
In the DCE mode, no buffers are used in the main link data paths, because
MX-2100 determines the receive and transmit rates.