PC Card components are those thin, rectangular products, shaped more or less like a thick credit card, that slide into the PC Card slots of notebook PCs (or desktop PCs that have a special adapter installed). Figure below shows an example of such a product, a Linksys adapter that handles both 802.11g and 802.11b wireless protocols.

On the far right of the figure is the portion that stays outside the PC Card slot, and this portion bears the Linksys logo as well as indicator lights called Power and Link.

The Power light, as you probably suspect, tells you that the adapter is getting power from the notebook (the card doesn’t have a separate power supply).

The Link light tells you if the card is receiving the wireless signal; as long as it shines a solid green, the card is communicating just fine.

Keep your eye on this light, though; if it starts flashing, the card is no longer communicating with a wireless transmitter on your network (usually the access point), in which case you’ll need to do some troubleshooting.

The more technically correct abbreviation for these components is PCMCIA (Personal Computer Memory Card International Association), but because nobody could come up with a decent way to pronounce that abbreviation, the industry understandably decided to adopt the phrase PC Card instead.

In fact, as PCMCIA developed and took on 32-bit capabilities, it became known as CardBus, and the vast majority of WLAN products on the market today designed for notebook use are of the CardBus variety.

Because CardBus is a 32-bit interface, it’s perfect for notebooks running 32-bit Windows platforms such as today’s dominant version, Windows XP (Professional or Home Edition).

Indeed, part of the success of wireless networking as a whole has been the ability of CardBus WLAN adapters to connect quickly and efficiently to the built-in wireless support offered in Windows XP.

In the case of WLANs set up to broadcast their SSID, and not to enforce encryption, connections from a Windows XP notebook with a CardBus adapter without proprietary protocols are practically automatic.

From a technical standpoint, the CardBus interface works nearly identically to the PCI (Peripheral Component Interconnect) interface common to today’s PCs. The signaling protocols are almost the same, and the two interfaces interact with the PC very similarly as well.

For WLAN equipment manufacturers, the similarities present the obvious advantage of being able to develop two types of component pretty well in parallel with one another.

Indeed, if you watch the release schedules of WLAN hardware from these companies, you’ll find that CardBus and PCI adapters come closely on the heels of one another (CardBus is usually first because its market is larger), while other types, such as USB adapters, come somewhat later.

Although you can certainly create a WLAN that consists of desktop PCs connected wirelessly to each other (ad hoc) or to an access point (infrastructure), such an architecture is extremely uncommon (although it’s certainly on the increase).

Partly because most PCs now ship with adapters for wired Ethernet networks, partly because wired Ethernet adapters are a fraction of the price of wireless adapters, and primarily because people don’t consider desktop PCs particularly portable, desktop PCs tend to find themselves wired to the network rather than beaming radio waves back and forth.

Given the greater speed and reliability of wired networks, this approach obviously makes sense.