Explore the world of FSK (Frequency-Shift Keying) modems in this 18-minute conference talk from the 36C3 ChaosWest event. Discover how these simple yet practical modems can be built with minimal effort, ranging from basic digital circuits to straightforward software solutions. Learn about their continued relevance in radio applications and data transmission through headphone outputs, despite the decline in telephone line data transfer. Gain insights into various implementation methods for FSK modems and be inspired to write code or pick up a soldering iron to experiment with this technology. Delve into the beauty of complex numbers and their practical applications in modem design. Join Christian Berger as he guides you through the fascinating realm of FSK modems, encouraging hands-on exploration and understanding of this enduring communication technology.