The evolution EM D1 from Sennheiser is a digital wireless receiver that can be used to capture audio when paired with an SK D1 bodypack transmitter and microphone or an SKM D1 handheld transmitter (sold separately) for live stage applications. The EM D1 is designed for reliability, sound quality, and user-friendliness. Under optimal conditions, you can simultaneously operate up to 15 individual ew D1 wireless microphone systems.