Etheric beam locator

An etheric beam locator was a device frequently carried by the Doctor. It was presumably used to locate etheric beams, and was also useful for detecting ion-charged emissions.

History
When captured by Kaleds on Skaro, the Fourth Doctor had an etheric beam locator in his pocket. (TV: Genesis of the Daleks) He later had it in London in 1889 (TV: The Talons of Weng-Chiang) and on Hephastos. (AUDIO: Babblesphere)

When faced with a bomb, the Sixth Doctor searched his pockets for an etheric beam locator. (AUDIO: The Condemned)

The Doctor later searched for a type 7 enhancer for his etheric beam locator. (AUDIO: The Raincloud Man)

While in Hexen Bridge, the Seventh Doctor had a sub-etheric beam locator in his pocket. (PROSE: The Hollow Men)

In Fortalice, Sam Jones and Gila traded a dismantled and useless etheric beam locator for some bread. (PROSE: The Scarlet Empress)

While on Janus Prime, the Eighth Doctor had a sub-etheric beam locator in his pocket. (PROSE: The Janus Conjunction)

The Tenth Doctor used one of these at one point whilst searching for an etheric energy emission. (PROSE: Needle Point)

Behind the scenes

 * The item that doubled as the Fourth Doctor's etheric beam locator in Genesis of the Daleks and The Talons of Weng-Chiang was (in real life) a Varian Klystron VA220 valve used in microwave transmission and oscillator equipment, such as television transmissions and radar technology.

Invalid sources
According to one account, "Dalek bumps" were in actuality etheric beam locators. Following his alliance with the tyrants of Skaro, an incarnation of the Master began to upgrade his aging body with "superior Dalek technology". This included not only a plunger for a hand, but also two etheric beam locators on his chest, which, to Emma and the Doctor's hilarity, resembled female breasts. Shortly thereafter, the newly-regenerated Thirteenth Doctor, finding herself in a female body for the first time, briefly mistook her actual breasts for etheric beam locators before she realised she had undergone a sex change with the regeneration. (NOTVALID: The Curse of Fatal Death)

An etheric beam locator was present on the TARDIS control console in the custom Minecraft-based desktop theme uploaded to the databanks of the Doctor's TARDIS by the YouTuber Ben as a surprise for Christel Dee. While attempting to stop the TARDIS from crashing, Christel remembered advice from her Type 40 Operational Handbook and successfully landed on the nearest planet by disabling the etheric beam locator, the food machine and the shield oscillators so as to reroute all the power to the temporal stabiliser and the thermocouplings. (NOTVALID: Doctor Who Minecraft)