Microscopy Image Gallery

Exploration of the Month

July 1998

phone cable


Cables, cords, wires, etc. . . We see them everywhere! They are connected to our televisions, computers, and toasters. Cables run around our house, between the walls, and down the street. But what do they do? The main function of a cable is to transmit power or information signals from one place to another. A cable contains what's called a conductor inside it. A conductor is a type of material which collects and transmits electricity. There are three main types of cables which are designated by their functions: electric power, electric telecommunications, and fiber-optic telecommunications.

Electric power cables are the means by which electricity reaches our homes and businesses. The power is transmitted through either copper or aluminum wires. These metals are chosen because of their high conductivity. Usually these wires are suspended in the air and twisted together for strength and stability. The metal strands in these cables have a large diameter to accommodate the huge quantity of power traveling through them.

The picure below shows a common elecrical cable. The metal which carries electricity is covered by a green, blue, or purple colored material called insulation. The insulation prevents the electricity from leaving the metal and reduces the likeliness of accidental shock. The larger black covering holds all of the smaller cables together and is called the sheath. The other pictures were taken with the scanning electron microscope. They illustrate the ends of the copper wires within the insulation.

electric power cable wire bunch with SEM singular wire with SEM

Electric telecommunication cables operate on the same basis as power cables, but their function and composition are much different. When people talk on the telephone, their voices aren't simply transmitted through the air to other people. The vibrations in their voices are changed into electronic data by an instrument in the telephone called the transmitter. Because the voice is now an electronic signal, it can travel across the wires. These cables require less power; therefore, their wire diameters are much smaller, usually less than 1/20 of an inch.

In the pictures below, the sheath is white with four smaller cables running through it. These smaller cables (brown, red, green, and yellow) house even smaller wires which are composed of seven metal strands. The metal in this cable is copper, shiny and similar in color to a penny. The copper strands actually carry the information.

whole cord w/ c-section inside white cord copper wires

Fiber-optic cables have only been used with regularity in the last two decades. Instead of metal, the cables are composed of many very small glass or plastic strands which carry information by using light, not electricity. Recently, fiber-optic cables have been in high demand. The lightning-fast speed needed for the internet works best with these cables. In 1988 the first fiber-optic cable was placed across the Atlantic Ocean, allowing quick transmission of information between continents.

assembly view of fiber-optic SEM 150X single fiber-optic strand

What does the future hold for cable? If you are at home, there is a good chance that your internet connection is established through the phone lines. Eventually, fiber-optic cables will be the standard for joining all information access, and they will replace the phone lines. One of the latest inventions is a cable called "firewire". Firewire is the next generation of information transmission. It contains six insulated cables within the sheath, four for information and two for electric power. Firewire may one day run throughout the entire house, allowing your VCR to be connected to the television and the computer - all in different rooms. Your entire house would work like a small computer network with every room having a connection!

Other Explorations

Minnesota Microscopy Society Web Pages maintained by Stuart McKernan
Comments, additions or questions may be addressed to MMS Webmaster

Questions? ... Comments? ...Short debates? ... email John Slanina, Project Micro Undergraduate Assistant
Last Updated: 7/21/98