Some Powerbooks took the 802.11b Airport Original card, described in this article:
802.11b unfortunately could not support anything but WPA1, and WEP encryption, both have been hacked.
An ethernet/WiFi 802.11g or faster wireless bridge is a better solution for those earlier Powerbooks.
Some Powerbook G4s support the Airport Extreme card:
The Extreme card for Powerbooks supports only 802.11g, at 33 Mbps maximum. Unless you depend on something for faster speed like certain AppleTV connections, or the fastest FiOS connection, or have many shared computers, you can change your wireless router to support both 802.11g and 802.11n with WPA2 encryption to maintain a good wireless network. 802.11n supports wireless speeds over 100 Mbps (with some slowdown with multiple shared computers).