Sennheiser Product Evolution Wireless G2 300 IEM Series General Description This evolution wireless monitoring system consists of a rack-mount transmitter and bodypack receiver with stereo earphones. Main features include 9 frequency banks with up to 12 presets each, a headphone output on the transmitter, and a switchable bi-boost and safety mode on the receiver to protect against excessive volume levels. The focus function allows the artist to find a customized balance between his or her own voice or instrument and that of the band.