The 803-EF8X Rotating Cam Limit Switch by Allen-Bradley is a heavy-duty circuit control switch used with industrial machines with repetitive operation cycles in applications where shaft rotation correlates with machine motion. The device, like every style EF series device, operates with a cam mounted on a rotating shaft which actuates contact as the shaft rotates, and it is designed for long-life and heavy-duty operation. The 803-EF8X comes with 8 cam-opened, 25A NC double break contact, with AC and DC contact ratings, and a spring-loaded cam-roller. The 803-EF8X has a ¾ diameter, rotating shaft, with 150 RPM base speed, and 8 cam assemblies operated independently, with adjustable lobes and valleys. When the shaft rotates the cam lobes press against the cam-roller activating the circuit, and when the cam valley passes by the cam roller, the circuit is deactivated. The 803-EF8X has a timing feature (when the rotating cam activates circuit) determined by the position of the cam on the shaft, and it has a dwell time (the amount of time for which the cam lobe activates the circuit.) determined by the size of the cam lobes.

The dwell time reaches its maximum limit when cam lobes are offset at the maximum angle, and it reaches its minimum when the lobes perfectly align. The device has an external dwell and timing adjustment option, located on the cover of the enclosure, and the adjustment can be done by using a screwdriver, even when the machine is still in motion. The 803-EF8X, unlike most Style EF devices, comes with a factory-modified double shaft extension instead of the standard Style EF left shaft extension, but it does have a standard Style EF 15 to 360 degrees, cam duration. The 803-EF8X has a working temperature range of -30 to 66 degrees Celsius (-22 to 150 degrees Fahrenheit), with a storage level of -30 to 93 degrees Celsius (-22 to 200 degrees Fahrenheit), and it has a NEMA Type 13 rated enclosure. It weighs about 20.4 kilograms (45 pounds), with a shipping volume of 441.3 x 158.8 x 242.1 millimeters (17.38 x 6.25 x 9.53 inches), and it is UL, CSA, and CE-certified.