View source

Making phone calls using an IP-PBX is not much different from traditional telephone systems.

The biggest difference is that with most SIP phones you have to press the "enter" key in order to dial the number. This is like making a phone call with your cell phone, where you also first enter the number and then start the call by pressing a button. Some installations have a dial plan on the phone, so that you don't have to push a button to start a call (this feature is only available in North America region with 10-digit national numbers). 

==Internal Number==
To call another extension, just dial the extension number. For example, if you want to reach extension 123 - just enter "123" and start the call. You will hear a ring back tone as soon as the other station starts to ring.

If "Camp On" is enabled on the system and the extension is busy or does not answer, the PBX will offer two options.
* The first option "1" tells the PBX to initiate a call back as soon as the extension becomes available again. This is the case if the extension finishes a call or turns DND off on the PBX. With this feature, you don't have to try again to reach this person; just wait until the PBX calls you back. You can have more than one callback pending; in this case the PBX will call you whenever one of the pending extensions becomes available again. 
* The second option "2" just sends the call to the mailbox. You may leave a voicemail message or go back to the operator, if that option has been enabled on the system. 

There are several services that your PBX system administrator may have programmed for you (like auto attendant and conference rooms) that can also be reached by dialing an extension number. You dial these numbers just like extension calls. 

==Dialing an Outside Number==
To dial an outside number, just enter the number that you want to reach. Please note that your system administrator may require a prefix before the number that you want to dial (for example "9"). On some VoIP phones, you may have a dial plan that automatically dials the number without requiring that you press the "start" key.

The PBX allows the administrator to assign an outside dial plan to each user. Depending on company policy, this feature may be used to restrict certain extensions from placing outside calls or from placing calls to expensive numbers.

If you are not in your office and your company has a strict telephone bill policy, you might want to tell the PBX that you want to bill an outgoing call to your extension number. This feature is useful if you are located in a room that has no permission to place outside calls, for example a kitchen. You must dial *91 to use this feature. The system will prompt you for your extension number, your access code and the destination number. 

==Receiving Incoming Calls==
Incoming calls are usually indicated with a ring tone. Calls from another extension sound different than calls from an outside line (depending on the phone model that you are using).

You should see the Caller-ID on your phone. If the Caller-ID is in your personal address book or in the domain's address book, the PBX will insert the name of the caller.