The 803-F412T Rotating Cam limit Switch by Allen-Bradley is a circuit control switch for heavy-duty machinery with dedicated operation cycles in an application where machine motion directly correlates to shaft rotation. It uses a cam that is mechanically mounted on a rotating shaft, and the mounting produces contact actuation as the shaft rotates. The device has a snap action contact block, with a contact mounted cam-roller, and 4 cam assemblies with adjustable lobes and valleys. The 803-F412T also has a rotating shaft with 150rpm of maximum shaft speed, with a keyway (slot) which connects the shaft to machines, and like most Style “F” series cam switches, it has an adjustable cam option. The 803-F412T circuit is activated as the cam lobe rides onto the cam-roller, opening Contacts 3 and 4 while at the same time closing Contacts 1 and 2. The snap action contact has a 10 A carrying current with AC MAKE/BREAK ratings of 12A/1.2 A at 600 Volts AC and a 0.1A maximum DC contact rating at 550 to 600 Volts DC.

The 803-F412T has a dwell time which is influenced by the length of the cam lobes, and it attains its maximum dwell time when the cam lobes are offset at the biggest angle, and its minimum dwell time is when the cam lobes align perfectly. It has a timing in degree, which is a function of the cam position on the shaft, with reference to a Top Dead Center (TDC), and it has a timing range of 12 to 348 degrees. The 803-F412T has internal cam adjustment options, and all of its available cams can be substituted for internally adjustable cams. The device can handle external dwell time and timing adjustments made by a screwdriver while it is in motion, and it has a default left shaft extension. It comes in a NEMA Type 1 and 13 rated enclosure, with an operating temperature range of -30 to 66 degrees Celsius (-22 to 150 degrees Fahrenheit), and with a -30 to 93 degrees Celsius (-22 to 200 degrees Fahrenheit) storage temperature range. The 803-F412T weighs about 5.4 kilograms (12 pounds) with overall dimensions of 179.4 x 82.6 x 312.7 millimeters (7.06 x 3.25 x 12.31 inches), and it has CE, UL and CSA certifications.