The 1746-NR4 module is a high-density digital input module. It provides four channels of sinking/sourcing, 120 Volt AC input. Each channel is individually isolated from the backplane and can handle a wide range of input signals, including AC and DC voltage signals.

The module's main purpose is to interface with various field devices such as switches, sensors, and other digital input devices, allowing the PLC to monitor their status and incorporate that information into its control logic.

To use the 1746-NR4 module, you would typically install it into a compatible Allen-Bradley rack chassis, connect the input devices to the module's terminal points, and then configure the module within the PLC programming software to map the input channels to the desired addresses and input types.