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.

When captured by Kaleds on Skaro, the Fourth Doctor had an etheric beam locator in his pocket. (DW: Genesis of the Daleks)

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

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

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

On Hyspero, Sam and Gila traded a dismantled and useless etheric beam locator for some bread. (EDA: The Scarlet Empress)

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

In an alternate timeline, the Master was outfitted with etheric beam locators, which resembled breasts. (DW: The Curse of Fatal Death)