US Patent 6838887 Proximity detection circuit and method of detecting small capacitance changes

Apparatus for dispensing paper from rolls which feeds continuously, roll to roll, and does not require extra procedure to bring stub roll into position. The apparatus holds and positions at least first and second rolls of paper with respect to each other; dispenses paper from the first roll; dispenses paper from the first and second rolls simultaneously when the first roll reduces to a predetermined diameter of paper, positions the depleted first roll for replacement without the necessity of removing the second roll; and dispenses from the second and replacement rolls simultaneously when the second roll reduces to a predetermined diameter of paper. The apparatus also has a proximity sensor, which senses when a hand is placed near the dispenser, and thereupon dispenses a set amount of towel. The proximity sensor incorporates “static” and noise immunity circuitry.