Williams AV DLR 400 ALK Digi-Wave 400 ReceiverThis is DLR 400 ALK receiver only. Transceiver is sold separately. The DLR 400 ALK uses alkaline batteries. The Digi Wave system is a digital spread spectrum (DSS), simultaneous two way wireless listening system. Using a 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. A Digi Wave