The SpeechLine Digital Wireless SL Bodypack DW-4-US from Sennheiser is an SL Series wireless transmitter optimized for speech. It can be used when paired with an optional wireless receiver and microphone in applications for meetings, lectures, conferences presentations where every word matters. In addition, it is compatible with all Sennheiser microphones such as the SL Headmic 1 or MKE 1 (sold separately). Featuring bi-directional communication between transmitter and receiver, the automatic frequency and interference management allows for convenient and reliable operation, which means the SL bodypack requires no settings to be adjusted. The LC display provides the link name, battery status and reception quality, and the easy-to-access mute-slider makes the use of the microphone very convenient.