A paging system with a number of central stations, each of which contains a number of pager apparatus associated with it. Each pager apparatus responds to one or more identifying numbers so that a caller may send a paging message to one or a number of pager apparatus, all of which respond to the same...http://www.google.fr/patents/US5473667?utm_source=gb-gplus-shareBrevet US5473667 - Paging system with third party authorization
