BY-WM4 Pro K1 is combining the revolutionary design and delivers an advanced 2.4 GHz wireless system that provides stellar, broadcast-quality sound. It can be used in any country and no need to worry about the band limitation. Practical functions and Versatility The transmitter comes with an Omnidirectional lavalier microphone, it can ensure a super clear sound when recording. The line-in provides the possibility for users to get more than one sound resource. A 3.5mm headphone output on receiver with level control lets you monitor the sound in real-time, even if your device lacks a headphone output.