Dynatherm HD250

See also a model 400 SERIE 1341 with a different panel: The triangle is reverse and the knobs are in different positions. The earlier models of de Forest were quite different in their look.

For the purpouse see Wikipedia Diathermy: "In the natural sciences, the term diathermy [di´ah-ther″me] means "electrically induced heat" the use of high-frequency electromagnetic currents as a form of physical or occupational therapy and in surgical procedures. The term diathermy is derived from the Greek words dia and therma, and literally means “heating through.” adj., adj diather´mal, diather´mic.

It is commonly used for muscle relaxation. It is also a method of heating tissue electromagnetically or ultrasonically for therapeutic purposes in medicine. Diathermy is used in physical therapy and occupational therapy to deliver moderate heat directly to pathologic lesions in the deeper tissues of the body.

Diathermy, whether achieved using short-wave radio frequency (range 1–100 MHz) or microwave energy (typically 915 MHz or 2.45 GHz), exerts physical effects and elicits a spectrum of physiological responses, the two methods differing mainly for their penetration capability.

Surgically, the extreme heat that can be produced by diathermy may be used to destroy neoplasms, warts, and infected tissues, and to cauterize blood vessels to prevent excessive bleeding. The technique is particularly valuable in neurosurgery and surgery of the eye. History: Diathermy was used for the first time in gynecology by the Spanish doctor Celedonio Calatayud in 1910.

Here you find 1 models, 1 with images and 0 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.
All listed radios etc. from Lee De Forest Laboratories, Ltd.; Los Angeles, California