Dive into the third installment of a video series on creating a playful telephony network using Asterisk PBX software and a Raspberry Pi. Learn to add custom extensions to the dialing plan, implement text-to-speech for dynamic messages, playback pre-recorded audio files, record user input, and incorporate variables and logic for conditional code based on time or call frequency. Master techniques such as creating custom dialplan extensions, using PLAYBACK for sound files, implementing SAYDIGITS and SET for number reading, utilizing PICOTTS for text-to-speech, creating a speaking clock, managing GLOBAL variables for call counting, setting up password authentication, and recording user responses. Perfect for those interested in building interactive telephone systems or escape room experiences.