When a programmable controller is built into the furnace as an integral component, the complete unit is generally classified as a furnace under this heading rather than being split between furnace and control-system headings. However, if the controller is imported separately or is a standalone industrial computer, it may warrant independent classification. CBP binding rulings are available to resolve ambiguous configurations before importation.

The heating mechanism is the key distinction: resistance furnaces generate heat through resistive elements energized by current, while induction furnaces induce eddy currents directly in the workpiece or a susceptor. This difference is reflected in separate SITC headings (74131 vs. 74132), and misclassification between the two can result in duty underpayment or overpayment. Technical specifications from the manufacturer confirming the heating method are the primary classification evidence.