Digital Link DL600E, User Manual

Page: 46 / 147

3-12 DL600E E1 Data Multiplexer UserÕs Guide
and the
CRC
values are compared. If they do not match, the
frame is considered bad and the
CRC
statistic is incremented.
Line Impedance
Ñ
75 OHM (BNC)
or
120 OHM (DA15)
(DefaultÑ
75 OHM)
Appears in
Menu-4
only when the remote unit is a DL600E unit.
The
Line Impedance
can be
75 OHMÑBNC
unbalanced or
120
OHMÑDB15
balanced.
Main/Alt Sync
Ñ
INT, EXT[
n
], NET,
and
DATA [1] (DTE)
(DefaultÑ
NET/INT)
Select the
E1
network transmitterÕs clock source. First specify
the
Main
clock source, then the
Alternate
. (Each clock source has
the same options.) Type
y
to conÞrm each action.
The
DL600E unit
always attempts to use the
Main
clock source. If
it is not available (due to a missing signal from the source or a
diagnostic test), it uses the
Alternate
source.
Select
NETWORK i
f the network is the clock source. If it is not,
select
INTERNAL
at one E1 end, and
NETWORK
at the other. Select
DATA
if the
DTE
is the clock source. If the
DL600E
unit is the
DTE
device
,
use a cable appropriate to your application
. When
neither the Main nor Alternate clock source is available, the DL600E
unit uses INTERNAL .
During all full bandwidth pattern tests, the DL600E unit cannot
use
NETWORK
timing. Typically, the remote unit is in network
loopback during a test and the DL600E unit should not use
NETWORK
timing since the received network signal is the signal
it is generating. In this case,
NETWORK
is overridden and
Alternate
(if available) or
INTERNAL
is used.
The clock currently in use appears on the screen in upper case letters.
In the example in Figure
3-2
, the local main and alternate clock in
use is
INT
while the remote main clock is NET (the alternate clock,
int, is not in use) .
In-Band Communications Bit
Ñ
4
to
8
(DefaultÑ
4)
Select a national bit (from
4
to
8)
in timeslot
0
for the in-band
4K
bps communications link with the remote unit. Digital Link
proprietary messages are sent to the remote unit using this bit.
G.704
recommends using bit
4.
(The unused national bits are set
to 1.) If this feature is disabled, all national bits are set to 1.