The Emergency Medical Holographic Channel was used to communicate with the EMH in USS Voyager's sickbay, via ship's computers. It was necessary, at first, because The Doctor was not designed to have access to ship systems as readily as other crewmembers. As The Doctor's holomatrix was enhanced and upgraded, enabling him to communicate more easily, the EMH channel fell into disuse. (VOY: "Parallax", "The Cloud", "The Thaw"}

This channel was also capable of being used to transmit intership messages. Tom Paris sent a discreet message to the Doctor while Voyager was under Kazon control. (VOY: "Basics, Part II")