The 803-E3 Rotating Cam Limit Switch is a Style E circuit control switch by Allen-Bradley that is used for control of industrial heavy-duty machinery with repetitive operational cycles, in long-life industrial processes where the machine motion directly correlates with shaft rotation. It operates using a shaft mounted cam, which actuates a Normally-Open (NO) contact as the shaft rotates, and the device is employed in industrial processes like waterway gate/lock operations, punch presses, steel forming/heavy metals, and packaging/assembling. It comes with 3 heavy-duty circuits with a cam-opened 25A Normally Open contact, 3 independent cam operators with adjustable lower and higher segments. The 803-E3 comes with a rotating shaft with a 150 RPM base shaft speed, and a keyway slot, used for connecting moving machine parts to the rotating shaft. It also has a contact-mounted cam-roller assembly, which glides against the adjustable rotating upper cam segments, activating the 25A NO contact in the process, and when the lower cam segment passes under it, the circuit de-activates.

The 803-E3 has a cam activation duration (dwell time), corresponding to the size of the upper cam segment, and a moment of activation (timing) corresponding to the position of the cam on the shaft, relative to the position of the key. The device can achieve its maximum dwell time when the upper cam lobes mechanically offset at the maximum angle, and it can achieve its minimum dwell time when they all align perfectly. The 803-E3 has a standard left shaft extension, and like every Style E series device, it has both dwell adjustments and external timing adjustments, located on the exterior of the enclosure. It comes in a NEMA Type 13 enclosure, and it has a working temperature range of -30 to 66 degrees Celsius (-22 to 150 degrees Fahrenheit), without impeding the contact operation. It weighs approximately 11.8 kilograms (26 pounds), with an aggregate volume of 274.6 x 158.8 x 242.1 millimeters (10.19 x 6.25 x 9.53 inches), and it has CE, CSA, and UL certifications.