The 803-A74RH Style A Rotating Cam Limit Switch is a circuit control switch by Allen-Bradley used with machinery with repeating operational cycles in operations where the machine’s motion corresponds to shaft rotating. The device is a Style A control switch in the Allen-Bradley Bulletin 803 heavy-duty series of cam limit switches, which uses a cam mounted on a rotating shaft which produces contact actuation as the shaft rotates. The 803-A74RH is built for long-term heavy-duty operations like the packaging, metal forming, and injection molding processes, and it is also built for rugged and harsh industrial environments. It comes with 7 heavy-duty control circuits with a cam-opened 25A Normally-Closed contact, and it has 7 independently operated cam operator assemblies, with adjustable lower and higher cam segments. The 803-A74RH also has a spring-loaded cam assembly, which is mounted on a contact base, and it has a rotating shaft with a 150 RPM base shaft speed, and a keyway (shaft slot), which connects moving machine parts to the rotating shaft.

The circuit is activated when the shaft rotates, and the cam lobe presses against the cam roller assembly, and when the cam valley passes through the cam roller assemblies, the circuit is de-activated. The 803-A74RH has a dwell time corresponding to the cam activation duration, and it is determined by the size and length of the cam lobe, and when the cam lobes align as the shaft rotates, the device achieves its minimum dwell time, and when the cam lobes offset the device achieves maximum dwell time. Like all Style A series devices, the 803-A74RH has internal adjustment settings for the dwell time and timing, and it has a set cam duration range of 14 to 346 degrees. It has an operating temperature limit of -30 to 66 degrees Celsius (-22 to 150 degrees Fahrenheit) without altering the contact performance, and it has storage temperature limits of -30 to 93 degrees Celsius (-22 to 200 degrees Fahrenheit). The 803-A74RH weighs around 24.5 kilograms (54 pounds), with shipping dimensions of 311.2 x 144.5 x 200 millimeters (12.25 x 5.69 x 7.88 inches), and it has CE, UL, and CSA certifications.