Hardware Reference
13
C613-03022-00 REV F
but at a reduced rate. The NSM should not be installed in a switch whose serial
number ends in the letter i or lower. The serial number is located on the
switch’s underside. For more information, including a sample serial number,
see “Compatible Base Units For NSMs” on page 5.
Figure 9: AT-AR048 NSM
DS3 Interface
The AT-AR048 NSM provides one standards-based unchannelised DS3
interface. The interface has the following features:
•
44.736 Mbit/s interface rate, 44.210 Mbit/s payload data rate
•
Separate transmit (Tx) and receive (Rx) BNC connectors
•
75-ohm impedance
•
B3ZS line encoding
•
Automatic compensation for lines up to 135m (450ft)
•
Loop or internal timing
•
C-bit framing
•
Support for PPP and Frame Relay encapsulation
The interface meets the following specifications:
•
ANSI T1.103, Digital Hierarchy - Synchronous DS3 Format
•
ANSI T1.107, Digital Hierarchy - Formats
•
ANSI T1.231, Digital Hierarchy - Layer 1 In-Service Digital
•
RFC 2496 (DS3 MIB)
DS3 Interface Cables
Use 75-ohm RG59 coaxial cables with BNC connectors. Two cables are
required, one for transmit and one for receive. Neither cable should exceed
135m (455ft) in length.
Testing a DS3 NSM
A Test Facility is built into all switch software. The Test Facility is designed to
test physical interfaces. The interface is not available for network operations
while the test is running.
For more information on the Test Facility’s operation, see the
Test Facility
chapter of the Rapier Switch Software Reference.
Loop
Activity
AIS
FERF
LOS
RX
TX
LOF
