Group call capability is provided as for a digital pager having a two word page address and using asynchronous detection. A group call is initiated by transmitting two identical binary words having an extra bit space between them, the binary word being word one of the individual paging address of each...http://www.google.com/patents/US4103286?utm_source=gb-gplus-sharePatent US4103286 - Digital binary group call circuitry arrangement
