Aurelia at 18 worked "the summer after high school [1924] in an insurance company, typing dull form letters eight hours a day five and a half days a week from wax dictation cylinders--a grim experience I vowed no child of mine would ever have to endure." [Letters Home, 3]. The woman in this 1920s photo is not Aurelia; she would not have been smiling. Aurelia Plath long remembered the sweltering office and cane-bottomed chair. [1]
In 1924, office air conditioning was decades in the future for most. The cylinders, in the photo conveniently racked, are cardboard coated with wax, and thus reusable. For those who don't remember, wax cylinders were first marketed for sound recording in 1889. While recorded music moved to discs, wax cylinders persisted in offices until after World War II. View a demonstration of a restored wax-cylinder dictation machine here. Basically, the boss spoke into a horn that scratched the sound of his voice onto a rotating cylinder, and the "Ediphone" operator, when ready to type out what he said, put that horn to her ear or maybe had a headset, like the lady in the photo, and controlled the playback with a foot pedal.
When working her part-time job at Massachusetts General Hospital (much easier than grimly writing or not writing), Sylvia Plath transcribed medical reports from a similar but updated dictation machine called an audiograph, commonly trademarked Audograph, that etched the boss's voice permanently onto vinyl discs. That job inspired Sylvia's stories "Johnny Panic and the Bible of Dreams" and "The Daughters of Blossom Street." In both, the business office is where fearful things happen.
[1] Aurelia to Max Gaebler, 7 June 1939. (Smith)