about Telephone

The oldest (and probably most common) use for a cabling system is to carry telephone signals.
In the old days, pairs of copper wires were strung throughout a building to carry the phone signal
from a central telephone closet to the individual telephone handsets. In the telephone
closet, the individual wires were brought together and mechanically and electrically connected
to all the incoming telephone lines so that the entire building was connected to the outside
world. Surprisingly, the basic layout for a telephone cabling system has changed very little. The
major difference today is that telephone systems have become digital. So most require a private
branch exchange (PBX), a special device that connects all the individual telephones together so
the telephone calls can go out over one high-speed line (called a trunk line) rather than over
multiple individual lines.
Generally speaking, today’s telephone networks are run along the same cabling paths as the
data cabling. Additionally, telephone systems use the same UTP cable that many networks
use for carrying data. They will usually share the same wiring closets with the data and television
cabling. The wires from telephone connections can be terminated almost identically
to data cabling.