Abstract: Sidewalls of cans from one filling and closing line are magnetized to provide each with a north pole oriented toward the can top. Sidewalls of cans from another filling and closing line are magnetized to provide each with a south pole oriented toward the can top. These tagged cans are randomly merged into one line for further processing without mixing up can top orientations, for instance, for cooking in a conveyor-fed continuous cooker in order to keep the cooker operating nearer full capacity. Then, each can passes a magnetic sensing station where one (top) end of each can is investigated by a probe which senses whether that end is a north pole or a south pole. The sensing station commands a diverter downstream which shunts the cans sensed as having north pole ends into a different line from the cans sensed as having south pole ends.

Abstract: The reader apparatus includes a clamp colocated with a photoelectric cell and lamp. A scale, e.g. calibrated in millimeters extends laterally from the photoelectric cell/lamp axis. A gas detector tube whose column of test particles is stained from one stain-starting end to a region part way therealong is clamped in the reader with its starting end of stain juxtaposed with the scale. The tube is manually moved axially until a portion of the lightest-in-color region is directly between the photoelectric cell and lamp. The transmitted light indicator is adjusted to align with one extreme on its scale. Then the tube is manually moved axially until a portion of the darkest-in-color region is directly between the photoelectric cell and lamp. The transmitted light indicator is adjusted to align with the other extreme on its scale. Finally the tube is slid axially until the indicator coincides with a preselected intermediate tick-mark, e.g. indicating a light transmittance value half-way between the two extremes.