In a world where video conferencing has become a norm, allowing participants to join via phone is an essential feature for many, especially when computer connectivity isn't possible. This tutorial covers how to achieve this using Vonage's Video API and Voice API, enabling users to dial into a conference number and enter a PIN to join the session. The process involves setting up a backend with Express and EJS templates, generating a random 4-digit PIN for each session, creating a SIP connection, and handling incoming calls via the Voice API webhooks. With the correct configuration and setup, participants can join a video session using their phone and enter a PIN to be heard by other participants in real-time.