Mobile wireless adapters come in three basic flavors: Bluetooth, Wi-Fi, and cellular. If you want to connect to a cellular network or to Wi-Fi access points, you need a wireless adapter to do so that is, unless your PDA has wireless capabilities built in. In addition to the type of wireless that an adapter supports, there is various adapter hardware to choose from, and not all PDAs support every type. You need to consider the compatibility of each type with your PDA.
The main types of adapters are Compact Flash (CF) and Secure Digital (SD). The next section covers these types in more detail but for now you need to know which type of card your PDA accepts to avoid buying the wrong one. The type of card slot your PDA is equipped with is usually listed on the package, in the user manual, and, for some devices, printed on the adapter slot.
Note: You can use CF and SD cards to provide storage or, in the case of wireless adapters, PDA cameras, and even PDA musk players, to add functionality to your PDA. The CF and SD standards describe the physical dimensions of the card and the electrical interface, not the card's function.
There are other types of cards, such as Type H and Type BI PC cards (PCMCIA), but these are not supported by the majority of PDA manufacturers. For a while, CF cards were the dominant adapter, but SD card adapters have caught up and may eventually surpass them in popularity.
Many newer PDAs have Bluetooth functionality built into them and a few even have integrated Wi-Fi, so you won't need to buy a separate adapter. If you choose a Wi-Fi-enabled PDA, pay attention to which standard it supports. An 802.11b or 802.llg PDA will be able to connect at more hotspots than an 802.1 la-enabled PDA will.
There are cellular adapters available for PDAs, too. These are usually CDMA, GSM, or GPRS. If you choose a cellular adapter, you will have the widest coverage and will be able to connect in more places than with Bluetooth or Wi-Fi, but you will also have to subscribe to a cellular carrier that supports the device you have purchased. If cellular is the way you want to go, choose a carrier first and then get the device.