12
Ethernet to G.703 Bridge
SW2-2
Option
Off
CRC-4 Disabled
On
CRC-4 Enabled
NOTE: When the data rate is set to 2.048Mb/s, then the unit is forced into
G.703 mode, and it transmits user data on all 32 time-lots. There is no framing
information; therefore, the CRC4 MF (SW2-2) switch is ignored. In all other
rate settings, the unit employs G.704 framing; TS0 is reserved for signaling.
Switch SW2-3 Data Inversion
Set Switch S2-3 to determine whether or not the data stream from the local DTE is
inverted within the Ethernet to G.703 Bridge before being passed to the
G.703/G.704 network. An inverted data stream may be required when you use the
Ethernet to G.703 Bridge to communicate with a G.703 device (that inverts the data)
on the remote end.In typical installations, data inversion is not necessary.
SW2-3
Option
Off
Data not inverted
On
Data inverted
Switch SW2-4: Remote Digital Loopback Type
The user can set this variable to select the type of remote loop that will be initiated
by the Ethernet to G.703 Bridge . If set to V.54, the Ethernet to G.703 Bridge will
initiate a V.54 loop when Remote Loop is selected by the front panel switches. If
set to CSU, the Ethernet to G.703 Bridge will initiate a CSU loop when Remote
Loop is selected by the front panel switches.
S2-4
RDL Type
Off
Initiate a V.54 RDL loop when selected
On
Initiate a CSU loopback when selected
SWITCH SW2-5 FRONT PANEL SWITCHES
As the Front Panel Switches may be inadvertently toggled, or in the event that the
end-user may not need to use the switches, the installer may disable the front panel
switches. Set Switch S2-5 to determine whether the front-panel toggle switches are
active or inactive.
11
Ethernet to G.703 Bridge
SW2-1 Line Coding: HDB3 (DEFAULT)
Use Switch SW2-1 to control the Network Line Coding options. Set these
options to be the same as the Line Coding given to you by
your Service Provider. If
you are using two Ethernet to G.703 Bridge s together as short range modems, set
both units to HDB3.
SW2-1
Line Encoding
OFF
HDB3
ON
AMI
OPTIONS:
HDB3, AMI
HDB3: In this line coding, the transmitter substitutes a deliberate bipolar
violation when excessive zeros in the data stream are detected. The receiver
recognizes these special violations and decodes them as zeros. This method
enables the network to meet minimum pulse density requirements. Unless
AMI is required in your application, HDB3 should be used whenever
possible.
AMI: Alternate Mark Inversion defines a pulse as a "mark,” a binary one, as
opposed to a zero. In an E1 network connection, signals are transmitted as a
sequence of ones and zeros. Ones are sent as pulses, and zeros are sent as
spaces, i.e., no pulse. Every other pulse is inverted from the previous pulse
in polarity, so that the signal can be effectively transmitted. This means,
however, that a long sequence of zeros in the data stream will cause
problems, since the NTU receiving the signal relies on the signal to recover
the 2.048 Mb/s clock.
If you must use AMI, you should ensure that the data terminal equipment
connected to the unit provides a minimally acceptable pulse density. For
this reason, there are advantages to using HDB3 instead. AMI coding does
not inherently account for ones density. To meet this requirement, the user
should ensure that the data inherently meets pulse density requirements.
SWITCH SW2-2: CRC-4 Multiframe
In framed mode, SW2-2 is used for CRC-4 MF. When CRC-4 is enabled, the unit
monitors the incoming data stream for CRC-4 errors. It transmits CRC-4 error
counts to the transmitting unit. When using timeslot zero (TS0), excessive errors
may cause loss of frame or loss of sync. If CRC-4 MF is used, both units must be set
for set for CRC-4 MF. Otherwise, the one using CRC-4 MF will detect loss of sync.
