Industrial chassis and card cages are metal frames that support and contain electronic components and power supplies. They usually include a backplane with slots for installing expansion boards, a power supply, cooling fans, and connectors. There are two main types of industrial backplanes: active and passive.

• Active backplanes contain bus control and motherboard circuitry; however, they do not contain processor complex components such as the central processing unit (CPU), chipset, or cache.
• Passive backplanes contain circuitry for bus connectors and, in some cases, buses and drivers.

Both active and passive industrial backplanes may also include bridges. For additional slots, an expansion chassis can be used.

Bus Types

Industrial chassis and card cages support active and passive backplanes of a specific bus type. There are many types of computer buses.

• Industry standard architecture (ISA) buses are I/O devices that can handle 16-bit data transfers at a clock speed of 8 MHz.
• Extended ISA (EISA), an enhanced version of the ISA bus, is capable of 32-bit data transfers.
• Peripheral component interconnect (PCI), a local bus system for high-end computers, can transfer 32 or 64 bits of data at a clock speed of 33 MHz.
• Compact PCI (cPCI) uses the electrical standards of the PCI bus, but is packaged in a Versa Module Eurocard (VME) bus.
• The VME bus (VMEbus) is a rugged, 32-bit device used in industrial, commercial and military applications. Variations include VME64, VME320, VME160, and VME extensions for instrumentation (VXI).
• Other bus types for industrial chassis and card cages include multi-system extension interface (MXI), embedded technology extended (ETX), embedded PCI extended (ePCI-X), advanced telecommunication computing architecture (AdvancedTCA), and host media processing (HMP).

Form Factor

Backplane form factor is an important consideration when selecting industrial chassis and card cages.

• Advanced technology (AT) is the original IBM motherboard design for personal computers (PCs). Full-size AT boards are up to 12” wide by 13.8” deep. By contrast, small or “baby” AT boards are only 8.57” wide by 13.04” deep.
• Low profile (LPX) backplanes mount expansion slots on a bus riser that connects to the motherboard.
• ATX combines features from the AT and LPX designs. Related technologies include MiniATX and microATX.
• NLX, another form factor for industrial backplanes, supports both current processors and technologies such as accelerated graphics port (AGP), universal serial bus (USB), and dual in-line memory module (DIMM). NLX cards are up to 9” wide and 13.6” deep.
• Other common form factors for industrial backplanes include Size A (100 mm x 160 mm), Size B (233 x 160 mm), Size C (233 x 340 mm), and Size D cards (360 mm x 340 mm).

Video Credit: Advantech Co., Ltd. / CC BY-SA 4.0

Other Specifications

Specifications for industrial chassis and card cages include mounting style, embedded cooling fans, number of CPU slots, switch and indicator options, and certifications. There are four basic mounting styles: rack mount, wall or ceiling mount, desktop, and tower.

Some industrial chassis and card cages have an on/off switch. Others have both an on/off switch and a reset switch. Visual or audible indicators notify users about hard disc drive (HDD) problems, CPU fan failure, chassis fan failure, or power failure.

Certifications indicate conformity with standards from organizations such as Underwriters Laboratories (UL) and the Canadian Standards Association (CSA).

Standards 

• IEC 60297-3-100 - MECHANICAL STRUCTURES FOR ELECTRONIC EQUIPMENT - DIMENSIONS OF MECHANICAL STRUCTURES OF THE 482,6 MM (19 IN) SERIES - PART 3-100:BASIC DIMENSIONS OF FRONT PANELS, SUBRACKS, CHASSIS, RACKS AND CABINETS
• IEC 60297-3-105 - MECHANICAL STRUCTURES FOR ELECTRONIC EQUIPMENT - DIMENSIONS OF MECHANICAL STRUCTURES OF THE 482,6 MM (19 IN) SERIES - PART 3-105:DIMENSIONS AND DESIGN ASPECTS FOR 1U HIGH CHASSIS
• IEC 61587-1 - MECHANICAL STRUCTURES FOR ELECTRONIC EQUIPMENT - TESTS FOR IEC 60917 AND IEC 60297 SERIES - PART 1: ENVIRONMENTAL REQUIREMENTS, TEST SET-UP AND SAFETY ASPECTS FOR CABINETS, RACKS, SUBRACKS AND CHASSIS UNDER INDOOR CONDITIONS