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BT Versatility
Installation and Maintenance Manual
45
Power fail
When planning the extension wiring for the system, consideration should be given to the use and location
of Featurephones and 2-wire extensions.
Analogue
In the event of a total system power failure, at least 50% of the equipped lines are switched to extensions.
Lines 1 and 2 are power-failed to extensions 26 and 27, the last two extensions on the basic unit. Line 5 is
power-failed to extension 34 and
Line 7 to extension 35, the last extensions on each of the expansion boards. These line positions are
summarised in the table below.
Note: If lines are power-failed to extension positions equipped with Featurephones, the user must replace
the Featurephone with a standard 2-wire phone to answer or make calls. FEATUREPHONES CANNOT BE
USED IN POWER FAIL.
Line position Power-fail extension
Line 1 Extn 26
Line 2 Extn 27
Line 5 Extn 34
Line 6 Extn 35
Line 9 Extn 42
Line 10 Extn 43
Line 13 Extn 50
Line 14 Extn 51
ISDN
In the event of a total system failure, the ISDN lines will not operate. ISDN devices can be connected
directly to the ISDN NTE or an external S bus, and work independently of the system.