Apple PowerBook G3 - Manual (Page 145)

145 Making Modem and Ethernet Connections to an Internal Expansion Card
2 Locate the adapter that came with your computer and connect the single end of it to the
card in your computer.
3 Prepare the Ethernet cable and telephone line as you would for a single connection of
either type.
4 Plug the modular connector from the Ethernet cable and the telephone cord into the two
sockets in the Y-adapter.
5 Start up the computer (if it is not already on) and set up your software to use the modem
and Ethernet connections.
Y-adapter
W Telephone connector
G Ethernet connector