It is a call which is made over internet protocol (VoIP). For example,
one can call using Google Voice to other recipient located miles away. Such
call can also be international.
“Call filter” allows blocking/unblocking the incoming calls as easy as to make filtration, it also journalizes all rejected calls. It is very convenient if you do not want to receive a call from some subscribers, when they will call you, “Call filter” will do so that your line is engaged.