Williams AV DLR 400 ALK Digi-Wave 400 Receiver Battery PoweredThe Digi Wave system is a digital spread spectrum (DSS), simultaneous two way wireless listening system. Using its frequency hopping algorithm, it avoids interference and is a very secure method of communication. The Digi Wave communication system allows users to listen and talk to one another wirelessly in a variety of scenarios. Great for use during training, presentations and tours, especially in houses of worship, classrooms, and healthcare