This read-write CvUriClassPattern object holds a regular expression used to match the phone-context attribute in a tel: URI, unused if left as a zero-length string, and mutually exclusive with cvCommonUriClassCfgURIPattern being set. Administrators use it to classify tel: URI calls by their numbering context in the same way the SIP equivalent does for sip: URIs. For example, an admin distinguishing between two numbering plans that could otherwise produce ambiguous phone numbers would rely on this pattern to correctly classify calls by context.