Question: What is a mandatory requirement for a User Equipment (UE) that supports Telephony in the context of Circuit Switched (CS) Core Network (CN) Domain?
Option 1: Support for premium rate services
Option 2: Capability to restrict emergency calls during roaming
Option 3: Enforcement of PIN code entry before initiating any call
Option 4: Support for Emergency Calls
Explanation: If a User Equipment (UE) supports Telephony, it is mandatory to also support Emergency Calls. This ensures all telephony-capable devices can initiate emergency calls, aligning with the CS CN Domain's requirement to support the emergency call teleservice.