The HU9 is designed for use with the Saramonic UwMic9 RX9 wireless, dual-channel, camera-mountable receiver. The RX9 allows you to record two people with their own wireless microphones by adding either a TX9 pocket transmitter and a clip-on lavalier microphone, a TX-XLR9 plug-on transmitter and an XLR handheld microphone, or a second HU9 handheld microphone. The combination mute button can be locked with a switch inside the housing to prevent the person holding the microphone from accidentally muting, changing the channel, or turning it off. A well-readable, backlit LCD display clearly shows the remaining battery life, mute status, as well as the group and its operating channel. A protective ring around the edge of the grille prevents the HU9 from rolling when placed on flat surfaces. The HU9 transmitter also features a selectable RF output power. With the "Low" setting, you can extend battery life in situations where the subject is close to the receiver. Medium and High are useful when the subject is further away or when using the HU9 in an environment with more potential interference.