Information Technology Reference
In-Depth Information
FIGURE A.3
An example of round non-paired wire.
Three or more wires may sometimes be wound in a loose spiral within the
jacket, but this is not the paired twisting that provides self-shielding. Round cable
may have either stranded or solid conductors. The common variations are the 4-
wire solid conductor cable used for inside residential wiring (called “4-wire,”
“inside wire,” “IW,” or “JK”) and the multiconductor cable used for RS-232 data
wiring. The 4-wire cable is famous for causing crosstalk when two phone lines are
installed on the same cable. If you are lucky, and your house is newer, you will have
telephone grade 4-pair wire. The older RS-232 terminal wiring could use nonpaired
wire because the data rate was very low (9600 bps versus 10,000,000 bps for
Ethernet!).
Flat cable is available in two common types: ribbon cable and flat jacketed
cable. Ribbon cable is a jacketless design where the insulation of each wire is joined
between the individual insulated, stranded conductors. Figure A.4 shows an exam-
ple of ribbon cable. The wires are laid side by side, forming a flat cable. The ribbon
cable may have an overlaying shield and outer jacket, although this is unusual.
Ribbon cables are often used for connections to circuit boards within equipment.
They generally are not used externally, because the lack of shielding exceeds FCC
emission standards.
An example of flat, jacketed cable is the common telephone cord used with
modular RJ-11 (style) and RJ-45 (style) connectorized equipment, as shown in Fig.
A.5. It is sometimes called “silver satin” or “telephone zip cord,” although it is
available in many colors and really doesn't zip apart to separate the conductors.
