What are the three service contents of navigation warning?

‌Air Traffic Control Service (ATCS): This is the core part of air traffic service and is divided into three main responsibilities:
‌Regional Control Service: Control of route flights.
‌Approach Control Service: Control of departure and arrival flights.
‌Airport Control Service: Control of activities in the airport area.
‌Flight Information Service (FIS): Usually served concurrently by regional control units, but in areas with large flight volumes and complex flight compositions, special agencies may be established to provide this service. The main responsibility of flight information service is to provide intelligence information required for various flights, including meteorological conditions, navigation facilities, route notices, etc., to help pilots make reasonable flight decisions.
‌Alerting Service (AS): When an aircraft is in search and rescue status, the alerting service will notify the relevant units and assist in handling emergencies.