Yealink UH37-DUO, Midlevel USB headset Duo. Professional-grade 35mm speakers, superb stereo sound, and dynamic EQ (Automatic switch between call mode and music mode), giving clear sound in call mode, high fidelity in music mode. Ultra-lightweight body, UH37 weighs about 15% less than the previous generation. When you're on the call, UH37's busylight will turn on automatically, or you can turn it on manually.