The phrase "a device whereby" is correct and usable in written English.
It can be used to describe a mechanism or method through which something is achieved or accomplished.
Example: "The invention is a device whereby users can control their home appliances remotely."
Alternatives: "a tool that allows" or "a mechanism through which".
It is a device whereby men in a group register with utter secrecy their true feelings-a truth detector.
His novel recalls his own disappearance and imprisonment but instead of relaying his experiences at first hand, Sarkohi invents a device whereby his main character is "possessed by the spirit of a former political prisoner" known only as number 612.
The modern concert is a device whereby formal, autonomous meanings are emphasized; further, the scope and available repertoire of the concert have been enormously increased through recordings, for any suitably equipped room may become, at the turn of a switch, a recital hall.
Topicalization is a device whereby the hearer's attention is focused on the occupier of a certain role.
A comic device whereby a panicky Joe or Louis delivers a line three times in succession — "What are you doing here?" or "Don't even get me started," with variations in wording and volume — is used at least four times in the episode.
In his first speech as leader, Pearson (recently returned from Oslo where he had been awarded the Nobel Peace Prize), moved an amendment to supply (a technical device whereby oppositions attempt to secure the government's resignation), and called, not for an election, but for the Progressive Conservatives to resign, allowing the Liberals to form a government.
A framing device, whereby troopers escorting the disgraced man's coffin on a train to Scotland start acting out his life, doesn't much help.
Settimia's songs make frequent use of dance rhythms and hemiola (a rhythmic device whereby pulses in groups of two occur simultaneously with pulses in groups of three), and they demonstrate a fluid melodic style.
ROBOTS came into the world as a literary device whereby the writers and film-makers of the early 20th century could explore their hopes and fears about technology, as the era of the automobile, telephone and aeroplane picked up its reckless jazz-age speed.
This is a quirky legal device whereby an ancient patent application resurfaces and can be used as a weapon against unsuspecting defendants.
"Magoo" also offers a curious framing device whereby the whole story is treated as a Broadway production, with Magoo as an actor portraying Scrooge.
