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Chapter A-Disconnection Causes
Polycom, Inc. A-7
ISDN Disconnection Causes
Table A-2 ISDN Disconnection Causes
Disconnection Cause
Number Summary Description
1 Unallocated
(unassigned number)
No route to the number exists in the ISDN network or the
number was not found in the routing table.
• Ensure that the number appears in the routing table.
• Ensure that it is a valid number and that correct digits
were dialed.
2 No route to specified
transit network
(national use)
The route specified (transit network) between the two
networks does not exist.
3 No route to destination No physical route to the destination number exists although
the dialed number is in the routing plan.
• The PRI D-Channel is malfunctioning.
• Incorrect connection of the span or WAN.
4 Send special
information tone
Return the special information tone to the calling party
indicating that the called user cannot be reached.
5 Misdialed trunk prefix
(national use)
A trunk prefix has erroneously been included in the called
user number.
6 Channel Unacceptable The sending entity in the call does not accept the channel
most recently identified.
7 Call awarded and
being delivered in an
Established channel
The incoming call is being connected to a channel previously
established for similar calls.
8 Pre-Emption The call has been pre-empted.
9 Pre-Emption – Circuit
reserved for reuse
Call is being cleared in response to user request.
16 Normal Call Clearing Call cleared normally because user hung up.
17 User Busy Dialed number is busy.
18 No User Responding The called user has not answered the call.
19 No Answer from User
(User Alerted)
Called user has received call alert, but has not responded
within a prescribed period of time. Internal network timers
may initiate this disconnection.
20 Subscriber Absent User is temporarily absent from the network - as when a
mobile user logs off.
21 Call Rejected Called number is either busy or has compatibility issues.
Supplementary service constraints in the network may also
initiate the disconnection.