Some of the reasons to employ call blocker functions are to avoid the hassle of persistent telemarketers or other telephone stalkers such as bill collectors, or to make sure the owner of the number is not forced to chat with nagging family members or other problematic persons such as disgruntled exes. The call-blocking service can also be used to prevent certain calls from phones used by minors.
Because a persistent ring can be disruptive and hard to avoid, call blocking allows the call to go directly to a service that explains that the person is not available. Various options are available as to the type of call blocking used, depending on the situation.
A user can select to block specific numbers or all numbers from anonymous sources that cannot be identified by caller identification. Additionally, priority ringing, in which certain numbers are identified by a specific ring, can also help the individual screen calls. Some services offer privacy manager functions in which the user has to identify himself before the call is allowed to go through. For protection of minors, some services feature functions in which all calls are blocked except those from callers who need a special code to get through. Smartphones often offer functions in their factory software or through downloadable software that allows the user to employ all these functions.