I've even got a 56 K modem inside !
I'm still looking for ideas...??
If your internet service provider makes dial-up service available, you can use the internal modem of your G4 Sawtooth to connect to the Internet on those occasions when high-speed service to your location gets interrupted. Albeit, the dial-up service won't be very fast, but sometimes it can be helpful while a high-speed service interruption is being remedied.
Also, you can then share that dial-up connection with another computer by connecting them with a FireWire cable.
In OS X 10.4.11 Tiger:
In System Preferences > Sharing, click on the Services tab. Then click to put a check mark in the check box to the left of Personal Web Sharing. Then click on the Start button. Next, click on the Firewall tab. In the Allow box, there should be another check mark in a check box to the left of Personal Web Sharing, if the Firewall is on. Then click on the Internet tab. To the right of "Share your connection from:", select Internal Modem from the drop-down menu. Under "To computers using:" click to put a check mark in the check box to the left of Built-in Firewire. Then click on the Start button. When asked whether you want to turn on Internet Sharing, click on the additional Start button.
In OS X 10.5.8 Leopard:
In System Preferences > Sharing, do not yet click to put a check mark in the check box to the left of Internet Sharing, but rather click on the words "Internet Sharing" to highlight that option. To the right of "Share your connection from:" select Internal Modem from the drop-down menu. To the right of "To computers using:" click to put a check mark in the check box to the left of Firewire. Next, click to put a check mark in the check box to the left of Internet Sharing. Then, when asked whether you want to turn on Internet Sharing, click on the Start button.
It might take some time before the second computer is able to access the Internet. I'm not sure how long it might take. Maybe it will be immediate, maybe it will be a few seconds, or maybe longer. Also, the Internet connection might get dropped occasionally, although maybe it won't either. If it does get dropped, stopping and restarting Internet Sharing has eventually worked for me.
In summary, your G4 can be used as a back-up means of connecting to the Internet in case of high speed service outages.