Paging systems typically include a network of ground stations or orbiting satellites equipped with transmitters and antennas for transmitting paging messages to small, battery-operated paging receivers that are worn about the person, known as pagers. Conventional pagers are receive-only devices and the...http://www.google.ca/patents/US6088593?utm_source=gb-gplus-sharePatent US6088593 - Two-way paging system and apparatus
