The Allen-Bradley 1746-A7 is a seven-slot SLC 500 rack assembly built to host up to seven backplane-connected I/O modules in a compact chassis, and it ships with a 1746-P1 power supply but no door. In SLC 500 systems, the first slot (slot 0) is reserved for the CPU or an adapter/network module, so the 7-slot chassis provides six usable I/O positions plus a CPU slot. This configuration—1746-A7 with the included 1746-P1 power supply and no door—serves as a mid-size rack option for Rockwell Automation's SLC 500 family, suitable for medium-scale automation setups requiring a modular, backplane-based I/O layout.
