The Allen Bradley 1746-A2 is an SLC 500 I/O Expansion Chassis with a 2-Slot expansion rack. It provides flexibility in an SLC 500 system configuration. The 1747 SLC processor, or the 1746 SLC I/O adapter module and the 1746 I/O modules are installed in this modular chassis.

The 1746-A2 chassis has dimensions of 5.5 x 7 x 4 inches and weighs 0.3 kilograms. It requires its own separate power supply which is fitted on the left-hand side of the chassis, has a backplane current up to 10 A at 5.1 Volts DC and 2.88 A at 24 Volts DC, and supports Back-Panel mounting with an open enclosure. This unit supports only a specific combination of SLC 500 1756 I/O modules; chassis interconnection cables are used for interconnecting up to 3 chassis for a maximum of 30 module slots. The 3-chassis assembly can be locally addressed by an I/O adapter or processor in the leftmost slot. A 1746-N2 card slot filler must be used to protect unused I/O slots in the chassis from dust and debris.

The 1746-A2 chassis is intended for use in non-hazardous locations. It has an operating temperature of 0 to 60 degrees Celsius (32 to 140 degrees Fahrenheit) and a relative humidity of 5% to 95% without condensation.