Body function panel
A dial was a type of device.
On the body function panels used aboard Constitution-class starships in the 2260s, there was one dial for each of the six health functions being measured. Each dial was a fixed scale with a moving pointer.
In 2265, tapping into his growing extrasensory perception powers, Gary Mitchell manipulated the dials on the panel monitoring him, so that they would show different measurements. When Gary put himself into a death state for twenty-two seconds, all dials showed him as "dead" with the pointers at the bottom of the scales. When he revived himself, the pointers returned to normal. (TOS: "Where No Man Has Gone Before")
In the final revised draft script for "Where No Man Has Gone Before", after saying that psychiatry was not an exact science, Gary Mitchell remarked how nice it would be if there was a dial measuring the level of sanity in a patient. [1]