A common problem in telephony is certain people in organizations want all their calls being screened, but 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 define who can call whom. This can be used to define who can call the boss and who can't. In this setting we can use patterns - for example, allow all extensions starting with 1, 2, 3, 4 or 5 to call the boss's extension:

We can also define who can call, even if a person is on do-not-disturb list. A common trick is to have the boss go on DND, set up a redirection to the person who 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; for all external calls, however, it would not differentiate between numbers. For our spouse 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 isn't. The spouse might not be SPAM, but everybody else may be for the boss's 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. The system can either consult external services for this, like TrueCNAM, or it can use the internal address book for making this decision. External services essentially provide a score from 0 to 100 about how likely the number is SPAM. These services work great for most numbers, but we have no control over the wife’s phone number. Who knows, maybe the service provider will believe it's 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's white-listed, the SPAM score is 0; if it is blacklisted it is 100 - otherwise we have a setting “SPAM score for regular address book entries” for this 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” - the score for anonymous callers can also 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 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 this 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 include to screen the call from the PBX. This isn't as cool as the Google SPAM detection with 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. The user can then 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.