SLC 500 I/O

SLC 500 I/O modules (Bulletin 1746) are the discrete and specialty input/output cards designed for Allen-Bradley SLC 500 modular chassis systems. The catalog number structure follows a consistent pattern: 1746 identifies the SLC 500 I/O platform, the next characters indicate signal direction and type — I for input, O for output — followed by a letter denoting output technology or input voltage class (A for AC, W for relay/dry contact), and a trailing number specifying the point count. For example, the popular 1746-OW16 is a 16-channel relay output module, while the 1746-OA16 delivers 16 points of AC output switching. The 1746-OW8 offers the same relay contact type in an 8-point footprint, and the 1746-IA8 provides 8-point 120 VAC discrete input capability. These modules seat directly into 1746-series chassis and are controlled through SLC 500 processors, making them a long-established choice for maintaining or expanding legacy SLC-based machine control systems.