How it all works
Prepaid long distance phone service begins with you. When you pick up your handset at the home or office, the device turns your voice into an analog signal, or electrical impulse, which travels along the wire. Digital signals are also available now, though analog is still widely used. The signal travels through a phone line composed of two copper wires originating in your house, which disappear into a box if you have underground wiring, or are suspended between poles near your house if you have aerial wiring. Near your house, your phone line will join with your neighbors' lines, and all these cables are spliced into a 25- or 50-pair wire. The analog signal travels along the cable, through the neighborhood, until it reaches another, bigger box, which is the junction connecting your neighborhood wires to the main line running past it.
The main line may be made of fiber-optics, co-ax, or copper wires. They all do basically the same thing, but some are ever more efficient and easier to obtain than others. The big box at the junction of the phone lines is powered or activated, and contains digitizers. It is here that your call joins the mainstream or multiplexed line ending in your local switch and the fiber-optic national network. So, your phone lines work much like your neighborhood streets emptying onto a large highway: like roads, there are smaller pathways or cables, that join up at a major intersection to meet with your national network or pathway, which connects you to the rest of the country, and the world.