Fax software enables a fax modem to send and receive faxes. A scanner should also be available for full fax capability. They are very common, since everyone who has a phone will have telephone lines in their home. Telephone lines used to be made of open wire, which was simply unshielded copper wire strung from place to place. Cable now replaces open wires as these had to be 12 inches apart in order to avoid electromagnetic interference.
Cable is insulated wire, and is used in a form called twisted pair.
Twisted pair consists of two pairs of twisted cable twisted around each other. Twisted pair can be bundled together so that more than a thousand pairs can be placed together. Telephone lines are cheap and fairly fast, but they are very sensitive to distance, and require repeaters or amplifiers every couple of miles to keep the signal strong when it is received at the other end. The bandwidth of twisted pair is about 1,000,000 hertz. Coaxial Cable Coaxial cable is a high bandwidth insulated cable.