A common problem in telephony is that certain people in organizations want all their calls being screened however a few have direct access. The boss’s wife should be able to call directly, while everybody else has to go through a screening process. How can we get this done using the Vodia PBX?

Internal Calls

Inside the PBX, we differentiate between internal calls and external calls that come from a trunk.

For internal calls we have permissions for each extension that defines who can call whom. This can be used to define who can call the boss and who not. In this setting we can use patterns, for example allow all extensions starting with 1, 2, 3, 4 or 5 to call the boss extension:

We can also define who can call even if a person is on do-not-disturb. A common trick is to have the boss go on DND, set up a redirection to the person that screens the calls and allow that person to call the boss. When the screening person goes home, the boss can push a button to get off DND and receive the calls directly.

The redirect on busy works well for internal calls, however for all external calls it would not differentiate between numbers. For our wife scenario, the permission setting where we list the extensions that may call the boss are better.

External Calls

For external calls, we essentially have to define what is SPAM and what is not. The wife might not be SPAM, but everybody else may be for the boss extension. Once the system knows what is SPAM it can take appropriate action, including rejecting and redirecting calls.

There are several ways to determine if a number is SPAM and what is the likelihood. The system can either consult external services for that like TrueCNAM or it can use the internal address book for making that decision. External services essentially provide a score from 0 to 100 about how likely the number is SPAM. Those services work great for most numbers, however we have no control over the wife’s phone number. Who knows, maybe the service provider will believe it is SPAM.

We can use the address book as the source for the ranking (in reg_recording.htm).

When a number is in the address book, there are three possibilities. If it is whitelisted the SPAM score is 0, if it is blacklisted it is 100 and otherwise we have a setting “SPAM score for regular address book entries” for that case in dom_settings.htm:

If we have selected the address book as the service provider, and the address book did not match the caller-ID, the system will use the “SPAM score for numbers not found in the address book”. Also, the score for anonymous callers can be defined. These settings are also available on extension level if needed.

So at the end of this process the PBX will come up with a SPAM score, hopefully 0 for the wife, 100 for numbers that were explicitly blocked in the address book and some value in the middle as set in the domain for everything else. In the next step the PBX will use that value to decide what to do with an incoming call to an extension.

For the call to the boss, we can choose a very low SPAM score value to reject calls and choose to be busy when a suspected SPAM call comes in (in dom_ext2.htm). This will trigger the redirect on busy rule, which we can use to redirect the call to a screening person.

Other choices are to screen the call from the PBX. This is not as cool as the Google SPAM detection with the automatic voice to text, but the PBX can also ask the caller to leave a short message which will then be played to the extension. Then the user can make a decision to take the call or not.

The user can now manage which external numbers get through to him by managing the address book. This is something many end users are able to do without having to ask support for help.

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