The MRD-70 AM/FM/CD Receiver with its RD-44 Display unit are the base foundation for an expandable multi-zone audio system. Additional RD-44 Remote Heads (RT-20 Router required) are easily connected through a single watertight DIN type cable, and create audio zones with remote control of audio functions from their installed location (bridge, galley, berth, etc.). Installation of an auxilliary amplifier in a zone allows for additional independent audio sources to be played and controlled in that zone. As many as 4 audio zones can be set up. The RD-44 Remote Heads include an intercom which will allow communication between stations. The unique mounting system for the waterproof display accommodates panel, pod or bracket mounting.] The RD-44 Remote Heads are designed to control the audio functions and sources of the MRD-70 marine radio. It features a backlit digital display and keypad that dim automatically at night. With versatile mounting options, the RD-44 can be installed up to 60 feet away from the radio in a variety of positions. Available in gray and black. The RT-20 Expansion Router is the connection module for expanding the MRD-70 or RD-44 to multiple zones. The watertight DIN connectors are easy to connect. Just plug and play up to three additional zones.