Group call is a service feature of radio services and mobile communications networks that allows a subscriber group or a closed user group(GBG) to be dialed by an individual. The group call represents a multipoint connection and can be used for voice communication as well as for data exchange.
Group calling is used in private mobile radio and trunked radio, but also in paging and in mobile radio networks such as the GSM network. In the latter, the mobile radio services Push-to-Talk( PTT) and Push-to-Talk Over Cellular( PoC) have been standardized by the Open Mobile Alliance( OMA).
In the case of BOS radio or Terrestrial Trunked Radio (Tetra), the group call can be made directly between the communication partners as a Direct Mode Operation( DMO), without using the switching technology. The group call is characterized by the selection of a group of persons with whom a subscriber wishes to communicate. After the connection has been established, communication is only possible in half- duplex mode for most services: Only one person can talk, all other participants listen.