Question: In a Voice Group Call Service (VGCS) scenario, when does the network request the calling service subscriber to join the voice group call channel as a listener via a channel release procedure?
Option 1: Immediately after the voice group call is established
Option 2: When the calling service subscriber is not actively talking
Option 3: After receiving an UPLINK_REL message from another mobile station
Option 4: Once the "uplink busy" flag is unset
Explanation: According to VGCS protocols, if the calling service subscriber is not actively transmitting (i.e., talking), the network will initiate a channel release procedure to have them join the voice group call as a listener. This ensures efficient resource allocation and allows other participants to engage in the conversation. The correct trigger for this action is the subscriber’s inactive talk state, making Option 2 the accurate choice.