Information Technology Reference
In-Depth Information
Check the jacks and sockets (for example, count the wires) be
fore plugging cables into your machines!
The amount of data that can be sent reliably over a cable in a
given amount of time (such as a second) depends upon what wires
are used, how connections are made, what controls might be present
to minimize interference, and what standards are involved in trans
mitting and receiving signals. Over the years, technology has
evolved regarding the capabilities that are possible for cables with
RJ45 jacks and sockets.
As already noted, the wire for use with RJ45 jacks and sock
ets contains four pairs of wires. Standards for connecting this
wire to jacks and sockets were first defined in 1991, but then ex
panded and refined in 1995. Standard wiring using the RJ45
jacks and sockets is said to be of type
Category 5
, or
Cat 5
.
For reference,
Category 1
refers to the standard for simple tele
phones prior to 1983 that involved two pairs of wires, or four
wires total.
How the eight wires connected to an RJ45 jack are used has
evolved considerably over the years, and three signaling standards
now apply to the same Category 5 wires and cables: 10BaseT,
100BaseT, and 1000BaseT. The earliest and slowest of these stan
dards was adopted in 1990 and is called
10BaseT
. Unraveling this
name somewhat,
10
designates that 10,000 bits of information can be commu
nicated per second.
Base
refers to a type of signaling called baseband signaling.
T
refers to the use of twisted pairs.
Although 10BaseT involves RJ45 jacks and the eight wires of
Category 5 cable, in fact only four of the wires (two pairs) are used
for communication. One pair is used to transmit data, and the sec
ond pair to receive data. (With only two of the four pairs of wires
needed for computer communication, some applications use the
