> Direct Inward System Access

Direct Inward System Access
Direct Inward System Access (DISA) connects callers using outside phone lines to
the PBX system. Callers obtain an internal dial tone as though they are connected to
the inside telephone system.This feature might be used by an employee who is out
of the office and needs to dial a long distance business number from his personal
phone without having to pay for it himself.The caller in this scenario would dial the
number allocated for the PBX DISA feature and use the PBX system as a hop to
place his long distance call.
Take proper security measures when configuring the DISA feature. Pass-code
authentication needs to be configured and provided by the outside caller in order to
get a dial tone from the PBX system.This feature should be monitored closely by
accounting reports to ensure that it is not being abused. In the interest of maintaining
accountability and satisfying audits, it is important to assign and periodically
change per-user codes for the DISA feature.



Unattended Transfer (or Blind Transfer)
Blind transfer exists when an end-receiver forwards a call to a different extension
and hangs up without verifying that the new destination party is available.This feature
is most likely to be used by an employee who has received a call by mistake.
The employee then advises the caller of the error and transfers him to the correct
extension.



Attended Transfer (or Consultative Transfer)
Compared to unattended transfer (blind transfer), an employee using attended
transfer speaks to or notifies the receiving party before transferring the call to them.
An example where attended transfer might be used is when a receptionist checks to
see if a party is available before connecting a call.


Consultation Hold
Consultation hold is defined by placing an active call on hold so that a second call
may be answered.This feature allows you to place a person on hold and consult with
a different party without hanging up the original call.You may switch between calls
as needed. Music on hold can be implemented with this feature to keep the caller
notified of the line’s activity.



No Answer Call Forwarding
No answer call forwarding allows calls to be forwarded to another destination, such
as a different extension or voicemail, when the called party is not answering.The
amount of time that it takes for a call to be forwarded can be implemented based on
seconds or number of ring tones.


Busy Call Forwarding
Busy call forwarding allows calls to be forwarded when the called party is otherwise
occupied.The called party could be handling another call or have initiated the Do
Not Disturb (DND) feature.



Do Not Disturb (DND)
The Do Not Disturb (DND) feature gives the end-system user the ability to ignore
incoming calls.The user activates the DND feature from her phone. DND functions
can be implemented in Ringer Off, Ringer Mute, Busy Mode, and Mixed Mode.
■ Ringer Off/Ringer Mute The call rings the extension without signaling
the ringer.The ringer is muted at the caller extension.
■ Busy Mode The phone extension acts as if it is off the hook. A busy
signal is sent to the PBX system from the end-user’s phone.
■ Mixed Mode Allows the phone extension to act in Ringer Off/Busy
Mode when standard calls come in. When priority calls come in, this mode
allows the caller to overwrite the DND feature and initiate normal ringing
of the phone.
NOTE
In Asterisk PBX default configuration, dialing *78 signals the PBX system to turn
on the Do Not Disturb feature, and dialing *79 disables it.
Figure 2.14 shows the Asterisk PBX DND feature in the debug window.This
feature is being initiated when the user dials *78.This PBX debug window shows
extension 2000 initiating a database update change to enable the DND feature with
DBput: family=DND, key=2000, value=YES command. Figure 2.15 shows similar
debug output from the Asterisk PBX, except this time user dialed *79 to disable
DND feature.The command DBdel: family=DND, key=2000 from the debug menu
deletes the DND for extension 2000.