The Emergency Holographic Program onboard the U. S. S. Voyager NCC-74656 uses an autonomous, self-sustaining mobile holoemitter that was made in the 29th century. The tiny device can perform all the functions usually performed by the arrays of holoemitters that are built into the ship's sickbay and holodecks. Technologically it is far more advanced than anything developed in the 24th century by Starfleet, and the crew have only a very basic understanding of how it works.

The mobile emitter is only a few centimeters in length, and is constructed from a smooth, gray metal. It has an independent power supply, and can store the entire EMH program and project the solid light hologram in almost any environment. This not only allows the EMH to move freely around the ship, but also allows him to leave it in order to accompany members of the crew on away missions. Although the holoemitter originated in the 29th century, the Doctor acquired it on a visit to the 20th century; it was one of several artifacts that had been appropriated by the entrepreneur Henry Starling when he found a crashed timeship. Starling down-loaded the Doctor from Voyager's computers and gave him the holoemitter to make him mobile. The holoemitter has a memory large enough to store more than one holographic program, but it appears that it can only project one hologram at a time. The visible interface consists of only a few controls, but they can be used to make adjustments to the Doctor's program. For example, when the crew were marooned on a Nyrian colony ship, B'Elanna Torres made adjustments to the holoemitter that effectively turned the Doctor into a tricorder. His optical sensors were reconfigured, increasing his optical resolution and allowing him to see energy signatures emitted from surrounding portals.

The holoemitter has some weaknesses. Its ability to project and store holoprograms can be affected by energy surges and radiation, and it can be deactivated by a sharp blow. Since the holoemitter does not appear to have a safety backup, if the Doctor's program is endangered he returns to sickbay and down-loads himself into the ship's main computers. The process of downloading the program from one system to the other takes only a few seconds. The process also works in reverse if Voyagers computers are damaged, the Doctor can protect himself by downloading his program into the holoemitter.



Mobile Holoemitter Casing Mobile Holoemitter controls