The 1746-A13 module is an analog input module that allows the SLC 500 PLC system to interface with analog signals in the real world. It provides 8 channels of single-ended analog voltage or current inputs, and each channel has a resolution of 10 bits. The input range for the voltage signals is typically 0 to 10 volts DC, and for current signals, it is typically 0 to 20 milliamps DC.

The module communicates with the SLC 500 processor through the backplane of the PLC system. The SLC 500 processor reads the analog input data from the module and uses it in the ladder logic program to control the desired process or system.

The 1746-A13 module requires a slot in the SLC 500 chassis for installation and connects to the backplane via a ribbon cable. It provides an easy and convenient way to integrate analog input signals into the SLC 500 control system.