The 803-B74RH Rotating Cam Limit Switch is a circuit control device by Allen-Bradley in the Style B Bulletin 803 Series of devices which are used with machinery with repetitive operational cycles and in industrial applications where machine motion correlates with shaft rotation. The device uses a shaft-mounted cam for operation and when the rotating shaft moves the cam actuates the contacts. The 803-B74RH comes with 7 heavy-duty control circuits, with a 10A snap action contact, and a contact-based cam roller assembly. it also comes with a rotating shaft with over-sized ball bearings and a maximum shaft speed of 150 RPM, and it has 7 independently-operated cam assemblies with adjustable lobes and valleys. The circuit is activated when the cam lobes push against the cam roller, and it is deactivated as the cam valley passes by the cam roller. The 803-B74RH has a keyway slot, which connects machines to the rotating shaft, and when the device is activated, the duration of the cam activation (dwell time) directly depends on the size of the cam lobe.

The 803-B74RH can achieve either a minimum or a maximum dwell time, depending on the angular alignments of the cam lobes, when the cam lobes align perfectly, the device will achieve the minimum dwell time, and when they offset at the maximum angle, the device achieves the maximum dwell time. The 803-B74RH has a cam timing depending on the position of the cam on the shaft relative to the position of the keyway and a cam duration range of 14 to 346 degrees. It comes with a modified right-hand shaft extension, unlike the standard left-shaft extension for the Style B series, and it has internal adjustments for both the timing and the dwell time. The 803-B74RH has an operating temperature range of -30 to 66 degrees Celsius (-22 to 150 degrees Fahrenheit), without affecting the contact control, and it comes in a NEMA Type 4 and 13 oil-tight and watertight industrial enclosure. It weighs about 15.9 kilograms (35 pounds) with total dimensions of 441.3 x 144.5 x 200 millimeters (17.38 x 5.69 x 7.88 inches), and it is CE, CSA, and UL-certified.