Question: In a Public Land Mobile Network (PLMN), what triggers a User Equipment (UE) to establish two-way radio communication with the network during a terminated call set-up when it's not already in communication?
Option 1: Receipt of call set-up information from the network
Option 2: Allocation of a traffic channel by the network
Option 3: Receiving its page message from the network
Option 4: Notification of proposed bearer capability information
Explanation: During a terminated call set-up, if the UE is not already in two-way radio communication with the network, the network initiates contact by sending a page message to the UE's known location area. Upon receiving this page message, the UE establishes communication with the selected cell, which is the trigger for setting up the call infrastructure (signaling and potential traffic channels). This highlights the role of paging in initiating communication for incoming calls in telecom networks.