ZyXEL Communications X6004 User Manual

Page of 334
Chapter 2 How It Works
X6004 User’s Guide
38
• FXO (Foreign Exchange Office) Trunk - This type of outbound line group consists 
of telephone cables connected to ports on an FXO interface card on the X6004. The 
telephone cables lead to the PSTN (Public Switched Telephone Network), or in other 
words your traditional (non-VoIP) telephone company. FXO ports always point in the 
direction of the telephone services. 
The figure below shows the relationship between FXS and FXO ports.    
Figure 5   FXS and FXO Ports  
• LCR (Least Cost Routing) - This is a rule which specifies which outbound line group is 
used when making an outbound call. It consists of a dialing condition, for example dial 0 
to make a call via a specific FXO trunk or dial 1 for calls via a SIP trunk. LCRs also set 
priority to which outbound line group should be tried first, second, third and so on when 
making outbound calls with the same dialing condition.
• Auto-Attendant - This is a feature which routes incoming calls to their proper extension. 
An auto-attendant is assigned to each outbound line group and it services incoming calls 
on those lines. If your organization has two outbound line groups, each with a specific 
telephone number for incoming calls, then you can assign a different auto-attendant for 
each incoming line. Assign one auto-attendant for general calls to the extensions in your 
organization (for example AA1) and one auto-attendant for direct routing to a FAX 
machine (for example FAX).
Figure 6   Auto-Attendant  
FXO
FXO
FXS
FXS
PSTN
AA1
FAX
1001
1002
1003
2001
555-0001
555-0002
Please dial the 
extension you 
would like to
reach.