Improvement to video-telephone systems allowing a called subscriber to have at his disposal on his television receiver screen, before he takes off his handset, information about the person who has initiated the call. Each subscriber station has a handset, a television camera, a television receiver and...http://www.google.com.hk/patents/US3946158?utm_source=gb-gplus-share專利 US3946158 - Video-telephone system initially signifies caller to called subscriber
