Sennheiser 505904 SL Headmic Set DW-4-US RCrystal Clear Speech Capture, Wirelessly Introducing the Sennheiser SL Headmic Set DW 4 US R, a professional digital wireless system designed specifically for speech applications. With automatic frequency and audio level management, this system ensures clear and reliable audio transmission without any hassle. Brand: Sennheiser Model: 505904 Type: Headmic Set Includes: SL Headmic 1, Rack Mount Features: Automatic Frequency Management, Automatic Audio