Features 3-11
3 Features C
Call Barring
Call Barring is a system programmable feature that can prohibit certain extension users from
making unauthorised toll calls.
Every extension is programmed to belong to one of 5 classes of service (COS). Each COS is
programmed to have a call barring class for day mode, night mode and lunch mode.
There are 5 call barring COS numbers available. Call barring COS number 1 is the highest
class and the COS number 5 is the lowest. That is, COS number 1 allows all toll calls. COS
numbers 2 through 5 are used to restrict calls by combining pre-programmed deny and
exception codes shown in the table on the next page.
Denied Codes
An outgoing outside call made by an extension with a call barring COS number between 2
and 5 is first checked against the assigned denied codes in program [302]-[305].
If the first digits of the dialled number (not including the line access code) are not found in
the class, the call can be made. Each class can store up to 20 denied codes, each consisting
of 11 digits.
Exception Codes
These codes are used to override a programmed denied code. A call denied by the denied
codes is checked against the selected exception codes assigned in program [306]. If a match
is found, the call can be made.
Up to 80 exception codes, each consisting of 11 digits, can be stored. The available number
of codes depends on the COS number.
• Emergency numbers, such as the police or fire station, should be stored in program
[309] “Emergency Dial Number Set” so that they are exempt from call barring.
• If a stored Host PBX access code in program [403] “Host PBX Access Codes” or a stored
carrier code in program [300] “Carrier Excepted Code Assignment”is found in the
dialled number, the subsequent telephone numbers will be checked for call barring.
• The interdigit timer assigned in program [208] “Interdigit Time” applies until the call
barring check is completed. When the timer expires, an outside outgoing call will be
disconnected while dialling, if “Enable” was selected in program [211] “No Dial
Disconnection”.
• The call barring class for a locked extension can be assigned in program [312] “Call
Barring – Extension Lock Boundary Class” so that even a locked extension can make a
local call, etc.
• It is programmable whether the “ ” or “#” the user dials is to be checked or not on the
Call Barring code in program [125] “Call Barring Check for and #”. This is useful to
prevent unauthorised calls which could be possible through certain Local Exchange
systems.
• Required System Programming
[301] Call Barring – System Speed Dialling Boundary Class
[302]-[305] Call Barring – Classes 2 through 5 Denied Codes
[306] Call Barring – Exception Codes
[601]-[603] Call Barring – Class of Service Assignment – Day/Night/Lunch
• Related Feature References
Emergency Call
Call Barring – Extension Lock Boundary Class
Call Barring for System Speed Dialling
Call Barring Override by Account Codes
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