Abstract: In a system of the type in which for call setup each circuit segment is selected from available circuit segments, at least one circuit segment is permanently reserved on each trunk between nodes needed to set up circuits for particular calls to or from preferred users, and circuit segments are dynamically allocated from the reserved segments for setting up a circuit from the terminal of one user who has a preferred user attribute for particular calls in the event of a call set-up request by one of the users in respect of a call for which he has been granted a preferred user attribute.

Abstract: A broadcasting method which can be used in an X.25 network. To transmit a block of information from a terminal to a broadcast module in the switch to which that terminal is connected, it consists of sending a call request packet from the terminal to the broadcast module of the switch to request the setting up of an X.25 virtual circuit between said first terminal and the broadcast module of the first switch, placing a broadcast request in one field of said call request packet, and placing the block of information to be broadcast in the data packets of the X.25 virtual circuit set up between said terminal and the broadcast module in response to said call request packet.