Black Box ME260A, Owner'S Manual

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34
MODULAR MODEM ELIMINATOR
3.3
Configuring Interface Modules
3.3.1 G
ENERAL
-P
URPOSE
I
NTERFACE
M
ODULES
Each general-purpose interface module has a DTE/DCE selector, designated SW1.
Figure 3-3 in Section 3.2.4 shows the position of the selector on each module, as
well as the location of the module-type marking. Set the switch in accordance with
the function implemented by the attached equipment.
3.3.2 ITU G.703 I
NTERFACE
M
ODULES
The ITU G.703 interface modules include jumpers that select the source of the
transmit clock signal.
Figure 3-4 in Section 3.2.4 shows the location of the jumpers.
G.703 64-kbps Co-directional Interface Module
The jumper that selects the source of the transmit clock has two positions:
• INT—the transmit clock is derived from an internal oscillator.
• LBT—the transmit clock is locked to the recovered receive clock (this mode is
called “loopback timing”).
The jumper that selects the data rate has two positions:
• 64 kbps—the module receives and transmits at 64 kbps.
• 128 kbps—the module receives and transmits at 128 kbps (not according to
the G.703 co-directional standard).
G.703 T1 and E1 Interface Modules
The jumper that selects the source of the transmit clock has three positions:
• INT—the transmit clock is derived from an internal oscillator.
• LBT—the transmit clock is locked to the recovered receive clock.
• EX—the transmit clock is locked to the clock signal provided by the
receive path of the other interface module installed in the Modular
Modem Eliminator.