G.703/G.704 NTU W/V35
11
2.3.20 SW1-8: E
NABLE
/D
ISABLE
L
OOP
T
ESTS
FROM
DTE
Use Switch SW1-8 to allow MT335A to enter loopback tests when the DTE
raises the appropriate loop request pin.
2.3.21 S
WITCH
SW2-1 L
INE
C
ODING
: 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 MT335As together as short range modems, set both units to
HDB3.
Options:
HDB3, AMI
HDB3
In this line coding, the transmitter substitutes a deliberate bipolar viola-
tion 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 require-
ments. 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
S1-8
Setting
Off
Response to DTE Loopback Request Enabled
On
Response to DTE Loopback Request Disabled
Position
Function
Factory Default
Selected Option
SW2-1
Line Coding
Off
HDB3
SW2-2
CRC-4 multiframe
Off
Disabled
SW2-3
Data Inversion
Off
Data Not Inverted
SW2-4
V.54/CSU select
Off
V.54 RDL loop
SW2-5
FPS enabled
Off
Enabled
SW2-6
V.54 Response
On
Disabled
SW2-7
Not Used
N/A
N/A
SW2-8
Not Used
N/A
N/A
SW2-1
Line Encoding
Off
HDB3
On
AMI
