Point-To-Point Circuits; Passive-Bus Or Multipoint; Fig . 5: Terminating Resistor Range - Nortel i2021 Series User Manual

Isdn teleset

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i2021 ISDN Teleset

Point-to-Point Circuits

A point-to-point application typically has the Terminating Resistors "On" at

both ends of the interface.

Fig. 5: Terminating Resistor Range

These may be new terms to you, so we will define them so you can better

understand their meaning. Passive Bus means that you can connect

several devices to the same Basic Rate Interface (ISDN line). Improperly

set Terminating Resistors account for many of the problems with ISDN

service. The "short version" of this explanation is that both ends of a bus

or circuit must be terminated.

Your choices of terminating resistance are two: none or 100 Ohms. The

idea is to terminate both ends of the bus. Set the resistors to ON at both

ends of the bus.

The best advice is to follow the instructions given by the NT1 manufacturer

and those of your terminating devices.

In the following configuration, the Terminating Resistors are "On" at both

ends of the interface. The resistors are on at the NT1 and "On" at the

farthest i2021 from the NT1.

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