DISA (Direct Inward System Access) allows someone calling in from outside the telephone switch (PBX) to obtain an "internal" system dial tone, and then dial calls as if from one of the extensions attached to the telephone switch.
 
While Switchvox does not allow for true DISA functionality, we do have features that allow for this type of configuration.  Here are the instructions for setting up DISA:
 
You will need to create an IVR with the following actions:

• Record Digits - This is for the password to secure the IVR.  Record the number of digits you want the password to be.  Set the digits recorded to a variable.

• Conditional Clause - Route the call to another IVR or back to this IVR if the caller does not enter the correct access code.

• Record Digits - If the caller enters the right code, then the call will continue to this action where they can record the number of digits for the number they wish to dial.  (Note: don't forget to account for 9 to dial out). Set the recorded digits to a variable.

• Send to External Number - Use the variable for the second record digits.  (Don't forget to configure what outgoing call rules this action should use.

Assign the IVR an extension number and point a DID at this extension.  You can now give out the DID number for customers do dial in to use the Switchvox to dial external numbers.