Where does the expression "dialled in" come from?

As an engineer, woodworker and model helicopter pilot I often hear the phrase "dialled in" to refer to a thing which has been perfectly set up.

Examples include: a table saw is dialled in when it has a perfectly square fence and a table which is perfectly aligned with the saw blade; a helicopter is dialled in when it is perfectly balanced and has the control input sensitivity "just right" for the pilot.

I was just wondering if anyone knows where the phrase "dialled in" came from? One wild guess is that it comes from the use of a dial indicator to make very small adjustments to achieve a high level of precision.

I'm not sure this idiom comes from a single source. Old radios had a "tuning dial" with an indicator for the frequency of the station that was "tuned in":

And "rheostats" (variable resistors) often had calibrated dials to permit them to be accurately set (and re-set back to the same point at a later time):

And similar knobs were used (and still are) on purely mechanical devices (eg, a metal lathe in a machine shop):

So, to "dial in" meant to adjust the knob (or knobs, for more complex devices) to achieve a desired setting.

I expect it comes from the use of a dial indicator when setting up mechanical equipment.

You use the dial indicator to measure very small distances. To get your equipment perfectly aligned, you set things up and then adjusted them by the dial indicator to get them "dialled in."

From there I expect it spread through the similarity of control dials to the original dial indicators.

This is similar to the existing answer from Hot Licks, but goes a step further back. Hot Licks refers to adjustment knobs as "dials." Before there were adjustment dials, there were dial indicators.