When a STUN IP phone is booted, what must the user enter to authenticate?

When a STUN IP phone is booted, the user is typically required to enter the extension number and voicemail PIN to authenticate. This process allows the phone to connect to the 3CX system and access the user's account associated with that extension. The extension number identifies the specific user or device within the 3CX infrastructure, while the voicemail PIN serves as an additional layer of security, ensuring that only the authorized user can access their voicemail and other associated features.

In the context of VoIP systems, the combination of the extension number and the voicemail PIN is a common method of authenticating users at the start. It facilitates seamless integration with the user's profile while providing a straightforward access point to the phone system.

This requirement is crucial as it directly connects the phone to the specific configuration and settings defined for that user in the PBX system, establishing the necessary link for the phone functionality.