Mobile Holographic Emitter

The autonomous self-sustaining mobile holo-emitter (in short: mobile emitter) is a piece of 29th century technology designed to remotely power and enable a single holographic instance away from in-garrisoned holoemitters. Constructed of a poly-deutonic alloy unknown to 24th century science, the mobile emitter is approximately the size of a human palm. (VOY: "Renaissance Man")

Origins

The Mobile Emitter

Owned by Henry Starling in 1996, the emitter was either aboard the appropriated Aeon timeship, or derived from the technology therein. Starling used the emitter to grant mobility to his captive, the Doctor, while the latter was displaced in time. After being returned to the 24th century by Captain Braxton, the USS Voyager was allowed to retain the anachronistic mobile emitter, granting the Doctor a newfound mobility and utility beyond Voyager's sickbay. (VOY: "Future's End, Part II")

Usage

The mobile emitter is a wholly self-contained holographic projector, generating the photons and force fields necessary to allow a hologram to physically interact with its environment. The emitter is either affixed to the exterior of the active holoprogram and thereby visible, or it can be covered or enveloped by the program, effectively hiding it from view. (VOY: "Renaissance Man")

Compatability

Eminently compatable with 24th century Federation technology, stored holographic programs (active and inactive) can be transferred to and from the emitter with ease—as simply as a voice command. (VOY: "Renaissance Man")

The mobile emitter's internal power source can also interact with a variety of other technologies to function as an impromptu battery. The Doctor's emitter was kept offline in 2375 while stranded inside a subspace sinkhole in the event it would be needed for emergency power. 15 years later (in an alternate 2390), after the emitter was rescued from the derelict Voyager, Harry Kim used it to power a stolen Borg temporal transmitter. (VOY: "Gravity", "Timeless")

Several Federation-designed holoprograms have interfaced with the Doctor's mobile emitter without difficulty, including the EMH from the USS Equinox, a holoprogram of Leonardo da Vinci, and Reginald Barclay's hologram of himself. (VOY: "Equinox", "Equinox, Part II", "Concerning Flight", "Inside Man")

Untoward functionality

The Mobile Emitter assimilated by Borg Nanoprobes attempting to assimilate a terminal console.

The mobile emitter assimilates a consoleIn 2375, a transporter accident resulted in the Doctor's mobile emitter being contaminated with nanoprobes. The probes assimilated the emitter, and after sampling Ensign Mulcahey's DNA, it built a maturation chamber and ultimately became embedded in the cerebral cortex of a highly-advanced Borg drone, designated One. After One's death, the mobile emitter was retrieved and returned to the Doctor for his use. (VOY: "Drone")