13. RF 1/2: The indicator will be illuminated when wireless microphone is on. 14. TONE: This control is used to adjust the bass, treble quality of the sound. The bass is decreased and treble is increased when the control turned clockwise. The bass is increased and treble is decreased when the control turned counter clockwise. 15. ECHO: Rotate the echo knob to your desired level. 16. Main Power: Press to switch the unit power to ON and OFF. 17. ANT. A/B: Receiving antenna of the wireless microphone. 18.