Mobile emitter The autonomous self - sustaining mobile holo - emitter , or mobile emitter , was a piece of 29th century technology designed to remotely power and enable a single holographic instance away from permanent holoemitter s . Constructed of a poly - deutonic alloy unknown to 24th century science , the mobile emitter was approximately the size of a Human palm . ( ) Origins . Owned by Henry Starling in 1996 , the emitter was either aboard the appropriated " Aeon " timeship , or derived from the 29th - century technology therein . Starling used the emitter to grant mobility to his captive , The Doctor , while the latter was displaced in time after he hacked into " Voyager " s computers and stole the hologram , as equipping The Doctor with the emitter gave Starling the ability to use him as a hostage by threatening to destroy the emitter as it held The Doctor ' s program . After being returned to the 24th century by Captain Braxton , the was allowed to retain the anachronistic mobile emitter , granting The Doctor a new - found mobility and utility beyond " Voyager " s sickbay and holodeck s , able to slip the emitter on and off relatively easily . ( ) Usage . The mobile emitter was a wholly self - contained holographic projector , generating the photon s and force field s necessary to allow a hologram to physically interact with its environment . The emitter was either affixed to the exterior of the active holoprogram and thereby visible , or it could be covered or enveloped by the program , effectively hiding it from view . ( ) The exact power source of the emitter was never revealed , but it would appear to be capable of operating in most conditions without charging ; during the alternate timeline of the Year of Hell , The Doctor was forced to rely on the emitter for the better part of a year after sickbay was destroyed in the first wave of the Krenim attacks , showing no sign that this was any kind of serious handicap to him and none of the crew expressing concern that the emitter ' s continued power supply might run down even as " Voyager " itself was left in increasingly battered condition by the Krenim attacks . ( ) In another alternate timeline , the entire ship was frozen on an ice planet for fifteen years after a crash - landing killed all on board , but once Chakotay and Harry Kim found the ship , they were able to reactivate The Doctor ' s program in sickbay and transfer him to the mobile emitter with no sign that the program or the emitter had suffered from over a decade on the ice planet ( ) . When The Doctor went on a solo away mission to a planet where time was moving at a rate of a day a second , he was essentially trapped on the planet for three years with only himself to rely on and the emitter apparently maintained his program perfectly well during that time , although this may have been due to the temporal anomalies of the planet meaning that the emitter was only operating for eighteen minutes from an outside perspective , or because The Doctor found a way to discreetly recharge it on the planet ( ) . Although a durable piece of technology , the emitter could be disrupted by certain conditions ; when " Voyager " spent a month passing through a nebula , prolonged exposure to the nebula ' s environment affected the emitter ' s ability to operate , and The Doctor ' s attempt to circumvent this issue by tying the emitter into the EPS manifold was only a temporary solution . ( ) Compatibility . Eminently compatible with 24th century Federation technology , stored holographic program s ( active and inactive ) could be transferred to and from the emitter with ease , as simply as a voice command . ( ) Although B ' Elanna Torres had some trouble understanding how the emitter worked , she was once able to reconfigure The Doctor ' s perceptions via the emitter in order to better scan their environment when " Voyager " was stolen by the Nyrian s and the crew trapped in their artificial biosphere . ( ) The mobile emitter ' s internal power source could also interact with a variety of other technologies to function as an impromptu battery . The Doctor ' s emitter was kept offline in 2375 while he was stranded inside a subspace sinkhole in the event it would be needed for emergency power . ( ) " Fifteen years later , after the emitter was rescued from the derelict " Voyager " in an alternate 2390 , Harry Kim used it to power a stolen Borg temporal transmitter after the transmitter ' s own power source failed , contacting Seven of Nine and preventing " Voyager " s crash , erasing this timeline . " ( ) Several Federation - designed holoprograms interfaced with The Doctor ' s mobile emitter without difficulty , including the EMH from the ( ) , a holoprogram of ( ) , Reginald Barclay ' s hologram of himself ( ) , Michael Sullivan ( ) , and the Hirogen hologram Iden . ( ) Untoward functionality . The hologram Marayna transferred herself into the sickbay ' s holo - emitters so that she could steal The Doctor ' s emitter in order to be able to leave the holodeck and roam around , despite the fact that she was being remotely operated by an outside controller . ( ) In 2375 , a transporter accident resulted in The Doctor ' s mobile emitter being contaminated with nanoprobe s . The probes assimilated the emitter , and after sampling Ensign Mulchaey ' 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 . ( ) In fiction . The Doctor ' s holonovel " Photons Be Free " had a fifty - kilogram backpack version of the mobile emitter – intended to reflect the burden of responsibilities that he faced – that the protagonist had to wear to leave sickbay on the . This version of the mobile emitter was one of the prominent features of " Chapter 5 - ' Out of the Frying Pan ' ( in which our protagonist must confront abusive colleagues ) " . ( ) Appendices . Background information . In the script of ( both the first draft and the final draft ) , the mobile emitter was described as " a thin , super - high tech band " which would be worn " across " the wearer ' s upper arm . Apocrypha . Another version of the mobile emitter was in the novel " " . In the book , Henry Bates , a holographic rights sympathizer , creates a functionally equivalent emitter about the size of a briefcase . In the " Department of Temporal Investigations " novel " Watching the Clock " , the mobile emitter ' s existence is one of the issues Janeway is questioned on after returning to the Alpha Quadrant , with DTI agents Dulmur and Lucsly criticizing her violation of the Temporal Prime Directive by using future technology so blatantly , only for Janeway to defend her decision by arguing that she wasn ' t going to deliberately handicap her chief medical officer for the sake of protocol . In " The Light Fantastic " , Data and Commander Geordi La Forge talk with The Doctor and Lieutenant Reginald Barclay about the possibility of replicating the emitter for general use , but The Doctor confirms that the emitter cannot be replicated by current technological standards . In " Takedown " , Admiral William T . Riker and La Forge are able to create a new mobile emitter while Riker has been augmented by the Cytherian s , allowing Riker to accompany Picard to confront the Cytherians by projecting an aspect of his consciousness into the emitter despite his body being ' confined ' to the Cytherian chair , but Riker gives the emitter to the Cytherians after the crisis is over as he feels using it would be a roundabout violation of the Prime Directive , as he could only assemble it using resources provided by the Cytherians . In the timeline of " Star Trek Online " , The Doctor filed a lawsuit against Starfleet to retain control of his mobile emitter , leading to a movement lobbying to establish civil rights for sentient artificial lifeforms , including holographic ( photonic ) projections and androids . The Soong Foundation develops a mobile emitter for civilian use , and photonic lifeforms equipped with mobile emitters serve on away teams alongside biological beings . Player characters can obtain photonic bridge officers with mobile emitters through a variety of means , including with Lobi crystal s ( obtained by opening " lockboxes " with keys bought from the game ' s store ) and through veteran rewards .