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BT Versatility
Installation and Maintenance Manual
19
System ISDN settings
The system can be configured with 8 Basic Rate ISDN interfaces. Half of these can be configured for
internal
S-bus operation.
The second interface on the CCU and each of the Ports Modules can be programmed as S-bus interfaces
for ISDN to-the-desk.
T
0
interface termination
An ISDN bus must be terminated twice, once at the start and once at the end of the bus. The Network
Terminating Equipment (NTE) will provide the termination at the start of the bus. The end termination is
also provided by the NTE if the BT Versatility is directly connected to one of the NTE RJ45 sockets.
If ISDN 2 extension cabling and sockets are provided between the NTE and the switch the end terminating
resistor will normally be provided by an ISDN type 2 RJ45 line jack.
In both of these cases BT Versatility T
0
interface does not require the terminating resistor to be connected
and the associated switches in the MDF associated with the T
0
interface must be set to OFF (Default).
NOTE:
In the case of structured cabling if no end termination is provided, the associated switches in the
MDF associated with the T
0
interface must be set to ON.
S
0
interface termination
An ISDN S-bus must be terminated twice, once at the start and once at the end of the bus. The BT
Versatility S
0
interface emulates the Network Terminating Equipment (NTE) and consequently is always
terminated with 100 ohm resistance. In this case the switches associated with the interface in the MDF
must be set ON.