3Com 3C10402B Administrator's Manual page 192

192 C 8: PSTN G
HAPTER
C
ATEWAY ONFIGURATION
The transmit pair on the PBX system must connect to the receive pair on
the NBX system, and the transmit pair on the NBX system must connect
to the receive pair on the PBX system.
To avoid timing issues, either the NBX system or the PBX system must
supply the link timing. Typically, the PBX system emulates the Central
Office (CO), and the timing mode is set to Internal and provides the
clock. In this case, set the timing mode of the NBX system to Loop.
1 On the NBX system, log in to the NBX NetSet utility using the
administrator login ID and password.
2 Click the appropriate link:
PSTN Gateway Configuration > T1 Spans
■
PSTN Gateway Configuration > ISDN PRI Spans
■
3 Click the appropriate span MAC address.
4 From the Timing Mode drop-down list, select Loop.
5 Click OK.
If the PBX system only supports Loop timing mode, then set the NBX
system timing mode to Internal.
A BRI line operates in TE mode, therefore the CO provides the timing
source.
If your configuration includes two NBX systems that are connected by a
T1 line, make sure that one system's timing mode is Internal and the
other system's timing mode is Loop.
The PBX system must use a protocol that the NBX system supports.
Configure the NBX and PBX systems so that they both use the same
protocol.
If your NBX system connects to the PBX system by means of an E1 or BRI
line, you must configure the ISDN PRI or ISDN BRI spans.
1 On the NBX system, click the appropriate link:
PSTN Gateway Configuration > ISDN PRI Spans
■
PSTN Gateway Configuration > ISDN BRI Spans
■
2 Click the appropriate span MAC address.