A telephone caller who cloaks his identity can't get through to a phone line that uses anonymous call rejection. His attempts to dial end with a recording that warns him to "decloak" his identity and try again. The Comcast Digital Voice phone service includes anonymous call rejection among its list of features you can use to make and manage contact. This screening option takes effect only if and when you want to use it.

Anatomy of Anonymity

In the early days of caller ID service, not all areas of the U.S. used telecommunications equipment that could transmit the information necessary to produce the identifier at the receiving end of a call. In some cases, neither name nor number appeared. As the service rollout proceeded, calls sometimes lacked an identifying name but transmitted the caller's number. Today's anonymous calls display no caller ID information when callers block it from appearing, either because of the nature of their business -- law enforcement, in some cases -- or in an attempt to disguise identity.

How to Become Anonymous

The hallmark of the anonymous call lies in its lack of caller ID information. Where you'd expect to see a name and a number on the display panel of your phone or caller ID box, only "Unavailable" appears, or a similar message. You can block your caller ID information by dialing "*67" after you hear a dial tone and before you enter your party's phone number. This feature, formally called caller ID blocking per call, applies on a call-by-call basis.

Blocking Anonymous Calls

If you prefer not to receive calls you can't identify, use the anonymous call rejection within the Comcast Digital Voice calling features. Unlike services such as call waiting, which your phone company must add to your line but which remains active full-time unless you block it for the duration of an individual call, you turn anonymous call rejection on and off yourself. Once you activate it, it remains active unless and until you turn it off using a separate procedure. The feature can't screen out calls that present falsified, or spoofed, caller ID information, only those that lack any ID at all.

Turning It On

As a Comcast phone subscriber, you can activate anonymous call rejection from your telephone. Pick up your receiver, or press "Talk" on a cordless phone, and wait until you hear a dial tone. Press "77" to turn the feature on. To deactivate it, press "87." The Xfinity Connect website (see Resources) gives you additional means of managing this and other calling features. If you use both Xfinity Voice and Xfinity Internet, use your Comcast ID and password to log into your Comcast account through the Email tab on the site's home page. From the Preferences tab, access the Call Manager and select "Call Screening." Use the "Anonymous Call Rejection" check box to turn the feature on or off. If you subscribe only to Xfinity Voice, click on the "Voicemail" tab to access your account.