ZyXEL Communications X2002, User Manual

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X2002 User’s Guide
35
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H A P T E R
2
How It Works
This chapter is an overview of different logical components and how they work
together to route calls on the X2002.
2.1 Call Routing
The two main functions of any IP-PBX are routing internal calls and handling calls
to and from the outside world.
The following sections explain how these functions are performed on the X2002.
2.1.1 Call Routing Terms
The following are some terms related to ZyXEL’s IP-PBX implementation.
• Extension - This is a unique number assigned to each telephone connected to
the X2002. Extensions are used to make calls between phones connected to the
X2002 and to route calls from the outside world to their correct target.
Extensions fall into the following two groups:
• SIP Extension - This is an extension assigned to a SIP (Session Initiation
Protocol) based IP phone connected to the X2002. Alternatively this could be
an extension assigned to an analog phone which connects to the X2002 via a
VoIP gateway device.
• FXS (Foreign Exchange Subscriber) Extension - This is an extension
assigned to an analog phone directly connected to a port on an FXS interface
card installed on the X2002 (See Figure 5 on page 36 .) The FXS ports on the
X2002 work the same way as the phone sockets in your home. In your home
you are a subscriber to the telephone services of your local telephone
company and when you connect an analog phone to the X2002 you subscribe
to the telephone services of the X2002.
• ISDN BRI (Basic Rate Interface) Extension - This is an extension
assigned to an ISDN phone directly connected to the X2002.
• Authority Group - This is a set of extensions. Each extension can only belong
to one authority group. Authority groups manage extensions by allowing them
to make only certain types of calls. For example, if you create two authority
groups, you can allow one group to make local calls and long distance calls and
the second authority group to make local calls only.