The 803-A4X Rotating Cam Limit Switch by Allen-Bradley is a circuit control device with a double shaft extension and a NEMA Type 1 rated enclosure. It is used with industrial machinery that has repetitive operation cycles in applications where the general machine motion correlates with the switch shaft rotation. It is used in operations with long-lived heavy-duty operations, and it makes uses of a cam mounted on a rotating shaft which produces contact actuation as the shaft rotates. The 803-A4X has 4 independently-operated cam assemblies, with adjustable cam segments (lobes and valley), and a rotating shaft with a 150rpm base shaft speed, and a double shaft extension. It also has a spring-loaded cam roller, mounted on a contact base, and with 4 cam-opened NC double-block circuit contact. the device’s rotating shaft is connected to moving machine part with a keyway (slot), and when the shaft rotates, the lobes brush against the cam roller, activating the circuit in the process, and when the valley passes by the cam roller, the circuit de-activates.

The 803-A4X has a dwell time (the timespan of its activation by the cam) which is directly determined by the length of the cam lobes, and the device can either have a maximum or minimum cam dwell time, depending on whether the lobes are offset at the maximum angle or whether they are aligned. The device has a timing measured in degrees, which is the point when the rotating cam activates the circuit, and it is a direct product of the cam position on the shaft relative to the keyway position. The 803-A4X has an internal timing and dwell time adjustment, and the internal settings of both the timing and the dwell time directly determine the machine’s operation. The device has a factory-ordered double-shaft extension, unlike most devices in the series, and it is enclosed with a NEMA indoor-rated enclosure. It has an operational temperature range of -30 to 66 degrees Celsius (-22 to 150 degrees Fahrenheit), with a storage temperature limit of -30 to 93 degrees Celsius (-22 to 200 degrees Fahrenheit), and it built for a rugged industrial environment. The 803-A4X weighs about 10 kilograms, with a shipping volume of 211.1 x 144.5 x 200 millimeters (8.31 x 5.69 x 7.88 inches), and it is CE, UL, and CSA-certified.