The device responsible for converting digital signals back to analog in telecommunications is called a digital-to-analog converter (DAC). DACs are crucial in various applications, including audio and video equipment, where digital data needs to be transformed into a waveform that can be perceived by human senses. They take binary values from digital systems and produce corresponding analog voltages or currents, allowing for seamless communication and interaction between digital devices and traditional analog systems. This conversion is essential for delivering high-fidelity multimedia experiences.