Reference Guide for the Model RT210/RT211 ISDN Routers
Ordering ISDN Lines C-3
Switch Types
Even with the development of National ISDN, it is still necessary to know what kind of switch
your telephone company uses locally, because National ISDN is still not available everywhere.
Even when it is, there are small variations in the way that different manufacturers implement
National ISDN.
To correctly order ISDN, you need to know the type of switch that is available in your area. For
Basic Rate ISDN, the most common types of switches and the differences between the switch
types are:
• AT&T 5ESS
AT&T 5ESS switches allow up to 8 devices to share the two B channels. You can configure
lines in one of three ways:
— Custom point-to-point
Custom indicates the use of AT&T’s proprietary standard.
— Custom multipoint
— National ISDN
National ISDN is multipoint.
You can order one or more directory numbers per basic rate ISDN line. We recommend that
you have only one directory number per line assigned to each router. If you also have other
devices attached to the line, they should each have their own directory number.
• Northern Telecom DMS-100 and DMS-250 Series
These Northern Telecom switches almost always have lines configured for National ISDN.
The following restrictions apply to Northern Telecom switches:
— A maximum of two devices can share the two B channels.
— Each of the B channels must have its own directory number.
— Lines from Northern Telecom switches are multipoint.
• Siemens EWSD
Siemens switches can support up to eight devices per basic rate line and lines are always
configured for National ISDN. You can order one or more directory numbers per line.
We recommend that you have only one directory number per line assigned to each router. If
you have other devices also attached to the line, they should each have their own directory
number.
NGRRT210.BK Page 3 Friday, October 17, 1997 2:37 PM