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).