Original AirPort: 802.11b wireless (11Mbps)
AirPort Extreme: 802.11g wireless (54Mbps)
Both systems are compatible in both directions. Old computers can connect to new base stations and vice versa. Of course, top speed is achieved only when both the computer and the base station are Extreme. (Note that both regular and Extreme are faster than your internet connection, so you will not notice any difference in browsing or download speeds.)
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