Presented By:
FAOZIAH
K.N.SUDHA RANI
L.MAMTA
VIJAY KUMAR UPADHYAY
TIKESHWAR PRASAD VERMA
OUTLINE
INTRODUCTION
TWISTED PAIR CABLING
COLOR CODING
JOINTING OF CABLES
INTRODUCTION
☼ A cable is two or more wires twisted together
to form a single assembly.
☼ It is used in the telephone industry to
connect lines from telephone exchanges
to pillars and from there to distribution
points (DP) and then to user sets, finally
connecting subscriber lines with the
exchange system.
☼ The heart of cable is the transmission
medium, which may be optical fibers or
twisted copper wire pairs. A mechanical
structure or jacket protects the medium
against the external environment.
Cable used in telecommunication system
INTRODUCTION
☼ Underground cables have pairs of copper
wire paired with the help of color coding. For
e.g. 5-pair , 10-pair, 20-pair, 50-pair, 100pair, 200-pair, 1000-pair, 1200-pair wire etc.
☼ In 5-1000 pair, the thickness of copper
wire is 0.6mm. In 1200 pair wire, the size is
0.4mm.
☼ Two types of underground cables laid in two
parts between exchange and telephone set :
- Primary cable (lies between main exchange
and pillar)
- Secondary cable (lies between pillar and
distribution points or DP )
Underground laying of Cable
TWISTED PAIR CABLING
☼ It was introduced by Alexander Graham Bell
in 1881.
☼ In twisted pair cabling two conductors are
twisted together (forward & return conductors)
for canceling out electromagnetic interference,
noise etc. from external sources.
☼ 1st wire - "tip" connected to the positive side of the circuit
2nd wire - "ring" connected to the negative side of the circuit
☼ The twist rate or pitch (twists per meter) is specific for given type of cable.
☼ Types of twisted pair cabling used –
FTP (foiled twisted pair)
STP (shielded twisted pair)
UTP (unshielded twisted pair)
UTP - primary wire type for telephone usage, it is not surrounded by any shielding.
COLOR CODING
☼ Color coding is a system in telecommunication wiring for identifying individual
conductors in twisted pair of cables, using different colors.
☼ The colors are applied to the insulation that covers each conductor.
☼ Each pair has five different ring wire colors but tip wire color depends on size of
cable though common in one 5-pair set.
5 – PAIR CABLE
☼ The most common is the 5 – pair twisted cable which contains five colors – Blue,
Orange, Green, Brown and Slate for the ring wire and white for tip wire common with
each ring wire making a total of 10 conductors.
COLOR CODING
10 – PAIR CABLE
☼ The next pair is the 10 – pair twisted cable which contains five colors – Blue,
Orange, Green, Brown and Slate in two sets for the ring wire and white and red
colors for tip wire of each set respectively making a total of 20 conductors.
COLOR CODING
20 – PAIR CABLE
☼ The 20 – pair cable has colors - Blue,
Orange, Green, Brown and Slate in 4 sets
for ring wire and white, red, black, yellow
colors for tip wire in each set making a
total of 40 conductors.
COLOR CODING
25 – PAIR CABLE
☼ The 25 – pair has similar four sets as
20-pair and a 5th set with violet colored
tip wire making a total of 50 conductors.
COLOR CODING
LARGE PAIR CABLE
☼ Large pairs cables include 50-pair, 100-pair, 800-pair, 1000-pair cables etc.
They follow the same color coding repeating ring and wire colors for specific sets.
For e.g.
200-pair cable -> 4 groups -> 50 wires each -> 5 sets -> 10 wires each -> 2 subsets
-> 5 wires each -> 5 ring colors and one tip color for each subset.
BINDER GROUPS
☼ For cables over 25 pairs, first 25 pairs (called binder group) are marked with
mylar ribbons using the color code starting with a white/blue ribbon, the second
25 pairs with a white/orange ribbon, and so on through the 24th binder group
(600 pairs), which has a violet/brown ribbon, and forming a "Super" binder. The
super binder is distributed in 100 pairs tied with a tip color coded ribbon. The
pattern then starts over.
☼ To more easily identify, which pair, a wire belongs to. Otherwise, one has to note
which color codes are physically twisted together.
JOINTING OF CABLES
NEED OF A STANDARD
☼ Important to follow standard construction practices and good workmanship.
☼ Difficulties to maintenance staff in tracing circuits at the time of faults if joined
haphazardly, also impairs the performance quality of the network
☼ Transmission properties can be maintained at satisfactory level when the
conductor jointing is done in perfect 1:1 order.
TYPES OF JOINTING
☼ Limited lengths available for different sizes of cables and occurrence of damage to
working cables resulting in a joint or two called Straight Joint.
STRAIGHT JOINT
☼ Operation on new or working cable made for diverting part of cable pairs to
another direction / area resulting in a Branch Joint.
BRANCH JOINT
JOINTING OF CABLES
☼ Transfer the cable pairs of one area in exchange (old pillar) to another area (new
pillar ) in same exchange or to transfer the cable pairs from existing exchange in the
area to another exchange (area transfer) results in a Tee Joint or Parallel Joint.
TEE OR PARALLEL JOINT
Old Exchange
New Exchange
JOINTING TECHNIQUE
☼ Same colored wires are jointed together by twisting them uniformly and dressing
with a sleeve. Gel/grease is pasted over the whole sleeve. Then, polythene is wrapped
over the greased sleeve which is again wrapped with tape to firmly hold polythene.
Cable pair is fitted in klastar (aluminum metal holder), then covered with a black
jacket. A metal channel is slided over the edge of the jacket and heated with a blow
lamp to firmly fix jacket. This procedure thus joins two wires according to standards.