Sony UWP-D21 Camera-Mount Wireless Omni Lavalier Microphone System High-quality sound with Sony digital audio processing True double tuner diversity for stable signal reception Auto gain mode volume control Channel memory for fast switching between receiver frequencies for two transmitter operation Transmitter frequency sent to receiver for matching multiple receivers to one transmitter Headphone output for monitoring Monitor mode for using a receiver as an ear monitor Variable muting function Receiver output level control High-visibility OLED display, ideal for indoor/outdoor use USB connector for power supply