Philips model 316X, 1940
This radio has a complicated electronic and mechanical layout to offer sophisticated short wave reception qualities, a successor of sorts to the type 291A.
The main (13-46m) short wave band can be fine tuned with a second tuning control. This wave band also employs a mechanical system of preselected bandspread regions. Pushing the second tuning control engages a gear rack, and rotation of the second tuning then selects one of the bandspread regions. At this stage, the main tuning control moves out and is disengaged. The applicable bandspread region is then tuned using the second tuning control. The main tuning control is re-engaged by cancelling the preselected bandspread region and pushing the main tuning control.
Calibration of the mechanically selected bandspread region is performed by adjusting the applicable one of 5 mechanical stops. These are accessible through a hole in the bezel after removing a threaded brass plug.