A telephony exchanges allows terminating equipment to indicate whether a telephone call is public, where the telephone conversation may be heard by more than one person at a remote end of a call, or private, where a person at the remote end of a call employs, for example, a handset or a headset. A calling...http://www.google.com/patents/US6795544?utm_source=gb-gplus-sharePatent US6795544 - Method for public conversation indication in a telephony exchange
