Editing Expansion card (section)

==Physical construction==
One edge of the expansion card holds the contacts (the edge connector or [[pin header]]) that fit into the slot. They establish the electrical contact between the electronics on the card and on the motherboard. Peripheral expansion cards generally have connectors for external cables. In the PC-compatible personal computer, these connectors were located in the support bracket at the back of the cabinet. Industrial backplane systems had connectors mounted on the top edge of the card, opposite to the backplane pins.

Depending on the [[Form factor (design)|form factor]] of the motherboard and [[computer case|case]], around one to seven expansion cards can be added to a computer system.  19 or more expansion cards can be installed in backplane systems. When many expansion cards are added to a system, total power consumption and heat dissipation become limiting factors. Some expansion cards take up more than one slot space. For example, many [[video card|graphics card]]s on the market as of 2010 are dual slot graphics cards, using the second slot as a place to put an active [[heat sink]] with a fan.

Some cards are "low-profile" cards, meaning that they are shorter than standard cards and will fit in a lower height computer chassis such as [[HTPC]] and [[Small form factor (desktop and motherboard)|SFF]]. (There is a "low profile PCI card" standard<ref name=":0">{{cite web|url=http://www.pcisig.com/specifications/conventional/conventional_pci/lowp_ecn.pdf |title=PCI Mechanical Working Group ECN: Low Profile PCI Card |publisher=Pcisig.com |access-date=2012-11-17}}</ref> that specifies a much smaller bracket and board area). The group of expansion cards that are used for external connectivity, such as [[network card|network]], [[Storage area network|SAN]] or [[modem]] cards, are commonly referred to as [[input/output]] cards (or I/O cards).