The Linksys WPC54G (compare prices) shown above is a typical PC Card network adapter for notebook computers. This adapter contains a very small built-in Wi-Fi antenna to provide wireless capability. It also features built-in LED lights that display the device status.
PC Card devices insert into a slot on the side of a notebook computer. Wireless adapters like the one shown typically protrude a small amount from the side of the computer; this allows Wi-Fi antennas to transmit without interference. In contrast, wired Ethernet PC Card adapters insert fully inside the computer.
Given the small space they fit into, PC Card adapters become very warm during normal operation. This is not a major concern as the adapters are designed to withstand heat. However, notebook computers provide an eject mechanism to remove PC Card adapters when not in use to protect them and possibly extend their life.