In order to establish a PPP link between two computers using the telephone line as medium for data transmission, you need to install (at least) one modem device in each computer. To install a modem device in computer you need to attach the modem hardware to the computer and later the telephone line to the modem hardware. To connect the modem to your computer, you need to connect the serial or USB cable that comes from the modem hardware to the appropriate input on your computer. To connect the modem to the telephone line system, you need to unplug the cable that connects your telephone device and plug it on the modem device, specifically in the port reserved for data transmission. Later, using a similar cable, you could connect your telephone device to the modem's telephone port, so you can realize telephone calls when no data transmition take place. To be on the safe side, do all the installation with the computer turned off. Then, when everthing has been put in place, turn it on. Once the system is up, you can verify the modem hardware using either the lsusb or lspci commands. These commands need to be run with administrative privileges, so probably need to sudo them or login as root user in order to execute thme. For example, assuming you are logged in as root user, and you are using an USB modem like that one we mentioned before, the output of lsusb command would look like the following: Bus 003 Device 001: ID 0000:0000 Bus 001 Device 001: ID 0000:0000 Bus 001 Device 002: ID 058f:6366 Alcor Micro Corp. Multi Flash Reader Bus 002 Device 001: ID 0000:0000 Bus 005 Device 003: ID 06e0:f104 Multi-Tech Systems, Inc. MT5634ZBA-USB MultiModemUSB (new firmware) Bus 005 Device 001: ID 0000:0000 Bus 005 Device 002: ID 046d:c018 Logitech, Inc. Optical Wheel Mouse Bus 004 Device 001: ID 0000:0000 The relevant line here is that mentioning the existence of a Multi-Tech System, Inc. MT5634ZBA-USB MultiModemUSB (new firmware) device. If the modem you installed doesn't appear in this list, it is probably because such hardware is not supported by &TCD;, yet. At this point, everything is ready for you to install and configure the computer either as server (see ) or client (see ).