It is possible for a user to make an outbound call via the Voicemail menu.

Dial 999 -> Enter PIN -> Press 9 (for options) -> Press 3 (to dial an external number) -> Dial external number.

When dialing the outbound number if no digits are entered for more than 1.5 seconds (1500ms) the PBX will assume the number is complete and start the outward dialing process.

To extend this timeout value, browse to “C:\Documents and Settings\All Users\Application Data\3CX\Data\Http\Interface\Ivr” (Windows XP/2003) or “C:\ProgramData\3CX\Data\Http\Interface\Ivr” (Windows Vista/2008), open the file called “VmailMenu.vxml”, and locate the lines:

<form id=”formDialOut”>
<var name=”external”/>
<field name=”fldDial”>

…and immediately after those lines, insert a new line:

<property name=”interdigittimeout” value=”5000″/>

This will set the inter-digit timeout to 5000 milliseconds (5 seconds).

Now you should save the changes and restart the 3CX Phone System service.