The 2020-D-US System from Sennheiser for installed applications, the SR 2020-D-US rack-mount transmitter, and the L 2021-40 charging unit can be used with HDE 2020-D-US receivers for assistive listening, visual description, and language transmission in conferences, museums, theatres, and houses of worship. The digital system transmits on up to eight license-free frequencies. The 2020-D-US has a switchable XLR-3 input, and up to eight transmitters can be combined. The SR 2020-D-US can be installed in a 19" rack and has a 1/4" headphone connector for monitoring. A backlit display shows the channel and the mic/line input level. The RF transmitter has a range of up to 80' indoors and 160' outdoors. The intelligent L 2021-40 charges the receivers in approximately two-and-a-half hours, accommodating up to 40 receivers. Ethernet connection and the included software provide for additional configuration and control.