Telephone Cables

 Solid PE Insulated & AP Sheathed (ALPETH) Air Core Cables to GR-421

Application

The cables are designed for use as subscriber distribution cables and as connection between central offices. The cables are suitable for installation in ducts, direct burial in the ground and also for aerial installation with integral suspension strand. An armoured option is offered for direct burial installations. A figure-8 self support option is offered for aerial installation.

Standards

• Telcordia (Bellcore) GR-421

Construction

     

Conductors: Solid annealed bare copper, 0.4/0.5/0.63/0.9mm, as per ASTM B-3/class 1 of IEC 60228
Insulation: Solid medium or high density polyethylene as per ASTM D 1248/IEC 60708
Twisted Pairs: Insulated conductors are twisted into pairs with varying lay length to minimize crosstalk
Cabling Element: Twisted Pairs
Cable Core Assembly:Cables with up to 400 pairs are composed of 25-pair units or 12/13-pair units; cables with over 400 pairs are composed of 50 or 100-pair units. Any extra pairs form a separate unit. Units are identified by colour coded binders. Construction is per GR-421 given in Cable Make Up Diagram.
Core Wrapping: One or more non-hygroscopic polyester tapes are helically or longitudinally laid with an overlap. These tapes furnish thermal, mechanical as well as high dielectric protection between shielding and individual conductors
Moisture Barrier: A layer of bare aluminium tape (0.2mm/8mil) is applied longitudinally with overlap over the cable core to provide 100% electrical shielding coverage and ensures a barrier against water vapor. In cables with more than 200 pairs, the aluminum tape may be corrugated for improved cable flexibility
Sheath: Black low density polyethylene as per ASTM D 1248/IEC 60708, being able to withstand exposure to sunlight, temperature variations, ground chemicals and other environmental contaminants
Ripcord: Ripcord may be provided for slitting the sheath longitudinally to facilitate its removal
Spare Pairs (optional): Spare pairs may be incorporated for large pair cables
Continuity Wire (optional): One tinned copper drain wire may be longitudinally laid to ensure electrical continuity of the screen
Optional Construction

Armoured Cable
0.15mm thick corrugated steel tape armour is applied with an overlap over an optional inner polye-thylene sheath. An outer polyethylene sheath is applied over the armour
Self-Support Cables
A 7-strand galvanized steel strand is used as support wire. Black polyethylene sheath covers both
core and support wire in a figure-8 construction

    

Aabbreviations

LAP (CAP):Copolymer coated aluminium tape + PE sheath
LAPSP (CAPSP):
LAP sheath + steel tape armour + PE sheath
AP (ALPETH): Bare aluminium tape + PE sheath
PAP: PE inner sheath + bare aluminium tape + PE sheath
PASP: PE inner sheath + bare aluminium tape + steel tape armour + PE outer sheath
ASP (STAPETH): Bare aluminium tape + steel tape armour + PE outer sheath
CACSP: Copolymer coated aluminum tape + copolymer coated steel tape armour + PE outer sheath
LAPSP: Copolymer coated aluminum tape +PE inner sheath + steel tape armour + PE outer sheath
FIGURE 8 LAP: Copolymer coated aluminum tape + PE outer sheath + self supporting

Electrical Properties

Nominal Conductor Diameter

mm

0.4

0.5

0.63

0.9

Conductor Gauge Size

AWG

26

24

22

19

Maximum Average DC Resistance

Ω/km / Ω/mile

140/225

87/140

55/88.6

27.0/43.4

Maximum Individual DC Resistance

Ω/km / Ω/mile

144.2/232

89.5/144

56.5/91.0

28.0/45.0

Minimum Insulation Resistance @500V DC

MΩ.km / MΩ.mile

1600/1000

1600/1000

1600/1000

1600/1000

Maximum Average Resistance Unbalance

%

1.5

1.5

1.5

1.5

Maximum Individual Resistance Unbalance

%

5

5

5

5

Average Mutual Capacitance nF/km / nF/kft

48.5-54.0 /14.8-16.5

48.5-54.0 /14.8-16.5

48.5-54.0 /14.8-16.5

48.5-54.0 /14.8-16.5

Maximum Individual Mutual Capacitance nF/km / nF/kft

57/17.4

57/17.4

57/17.4

57/17.4

Maximum Individual Capacitance Unbalance pair-to-pair pF/km / pF/kft

145/44

145/44

145/44

145/44

Capacitance Unbalance RMS pair-to-pair pF/km / pF/kft

45/13.7

45/13.7

45/13.7

45/13.7

Maximum Individual Capacitance Unbalance
pair-to-ground
pF/km / pF/kft

2625/800

2625/800

2625/800

2625/800

Maximum Average Capacitance Unbalance
pair-to-ground
pF/km / pF/kft

574/175

574/175

574/175

574/175

Maximum Conductor Loop Resistance @20°C Ω/km / Ω/mile

300/482

192/309

114/183.6

60/96.4

Impedance @1KHz Ω

994

796

660

445

Impedance @100KHz Ω 147 134 125 122
Impedance @512KHz Ω 120 118 117 116
Impedance @1MHz Ω 117 115 114 113
Maximum Average Attenuation @0.8KHz dB/km / dB/kft 1.64/0.5 1.30/0.39 1.04/0.32 0.74/0.22

Maximum Average Attenuation @1KHz

dB/km / dB/kft

1.68/0.51

1.35/0.41

1.08/0.33

0.76/0.23

Maximum Average Attenuation @3KHz

dB/km / dB/kft

3.18/0.97

2.52/0.77

2.01/0.61

1.42/0.43

Maximum Average Attenuation @150KHz

dB/km / dB/kft

11.4/3.47

8.3/2.53

6.2/1.89

4.4/1.34

Maximum Average Attenuation @772KHz

dB/km / dB/kft

24.3/7.4

19.4/5.9

15.4/4.7

10.8/3.3

Maximum Average Attenuation @1000KHz

dB/km / dB/kft

27.1/8.25

21.4/6.52

17.5/5.33

12.8/3.89

Dielectric Strength

 

 

 

 

 

Conductor to Conductor (3secs) V DC

2400

3000

4000

5000

Conductor to Conductor (3secs) V DC

10000

10000

10000

10000

Minimum EL Far-end Cross-talk-Mean Power Sum          

@150KHz

dB/305m / dB/kft

61

63

63

65

@772KHz

dB/305m / dB/kft

47

49

49

57

@1.6MHz

dB/305m / dB/kft

41

42

43

44

@3.15MHz

dB/305m / dB/kft

35

37

37

39

@6.3MHz

dB/305m / dB/kft

29

31

31

33

Minimum Far-end Cross-talk-Worst Pair Power Sum          

@150KHz

dB/305m / dB/kft

57

57

57

59

@772KHz

dB/305m / dB/kft

43

43

43

45

@1.6MHz

dB/305m / dB/kft

37

37

37

39

@3.15MHz

dB/305m / dB/kft

31

31

31

33

@6.3MHz

dB/305m / dB/kft

25

25

25

27

Minimum Near-end Cross-talk-Mean Power Sum          

@150KHz

dB/305m / dB/kft

58

58

58

58

@772KHz

dB/305m / dB/kft

47

47

47

47

@1.6MHz

dB/305m / dB/kft

43

43

43

43

@3.15MHz

dB/305m / dB/kft

38

38

38

38

@6.3MHz

dB/305m / dB/kft

34

34

34

34

Minimum Near-end Cross-talk-Worst Pair Power Sum

         

@150KHz

dB/305m / dB/kft

53

53

53

53

@772KHz

dB/305m / dB/kft

42

42

42

42

@1.6MHz

dB/305m / dB/kft

38

38

38

38

@3.15MHz

dB/305m / dB/kft

33

33

33

33

@6.3MHz

dB/305m / dB/kft

29

29

29

29

Nominal Insulation Thickness

mm

0.175

0.2

0.26

0.3

Nominal Insulated Conductor Diameter

mm

0.75

0.9

1.15

1.5

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