Black Box ME260A, Owner'S Manual

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12
MODULAR MODEM ELIMINATOR
2.2.4 T
IMING
O
PTIONS FOR THE
I
NTERFACE
M
ODULES
The timing options offered by the Modular Modem Eliminator depend
on two factors:
• Types of interface modules installed in the Modular Modem Eliminator
(general purpose, or ITU G.703), and the settings on these modules.
• Modular Modem Eliminator operating mode.
This section covers the timing options offered by the various interface modules.
For information on the timing options available in each operating mode,
refer to Sections 2.2.5 and 2.2.6 .
General-Purpose Interface Modules
The timing mode of a general-purpose interface module is selected via the
DCE/DTE switch of the module:
• DCE—the interface module supplies clock signals for the receive and transmit
paths. For the X.21 interface, the module provides only a transmit clock signal,
and expects to receive data from the DTE at the same rate.
Figure 2-1 shows
the flow of timing signals for the DCE mode.
Figure 2-1. Flow of timing signals for DCE mode.
Interface Module
(DCE Mode)
Transmit Clock
Transmit Data
Receive Data
Receive Clock
RD
RC
TD
TC