OVERHEAD CONSTRUCTION
AERIAL CABLE - SELF SUPPORTING

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Multicore underground cable was introduced early on in Telecommunications but aerial cable was not used that much.  This was probably due to the cost of producing small quantities and the technology involved in hanging such a cable.  The obvious way to hang a cable in those days was the catenary wire, where a steel wire is suspended, between two points and a cable attached to it.

The GPO used this idea and attached the cable by various forms including the use of a lashing machine which wrapped a wires around both the catenary wire and the multicore cable.

In the 1950's the catenary wire became integral to the multicore cable and self suspended aerial cable was thus formed.

Erection of aerial cable was more difficult than small gauge open wires and specialist equipment was designed to assist.

This cable was generally used in rural areas where undergrounding cables was expensive or impossible.

PO ENGINEERING INSTRUCTIONS
LINES
OVERHEAD
F 1191
Issue 1, Sept. 1970

AERIAL CABLING
Cable, Aerial, Self-supporting, Combined
Description and use

1. General
This Instruction describes aerial cables with integral suspension strand and the fittings used with the cable. Conditions of use are also given.

For information on construction practices when using this type of cable see F 3191.

In view of the large quantities existing in the field, information on superseded-fittings is given in paragraph 7.

2 Cable, Aerial, Self-supporting, Combined
This type of aerial cable is used for overhead distribution when more than two subscribers lines are required see F 1051. It is also used for the replacement of open wire and mixed open wire/ drop wire routes.

The sheath is polythene and the cable core is equivalent to that of Cable, Polythene, Twin, as described in Underground, F 1058. Details of cable size, maximum external diameter of the core, and total weight per yard, are given in the Vocabulary of Stores.

(NOTE:- Except for a limited trial quantity, aluminium conductors will not be used in aerial cable for the present.)

3. Cable, P.C.Q.T.A.
This cable is used on aerial junction routes. The sheath is of black polythene and the conductor insulant is paper.  The core, which is equivalent to that of Cable, P.C.Q.T., as described in Underground, F 1058, is enclosed in an aluminium foil water barrier. The cable is manufactured in accordance with Post Office Specification CW222 and the sizes of cable available are given in the Vocabulary of Stores.

4. Suspension Strands
4 and 7 pair cables contain a single 12 S.W.G. (1/12) galvanised steel suspension strand of 1,320lb. breaking load. Larger cables have a seven stranded 16 S.W.G. (7/16) galvanised steel suspension strand of 3,520lb. breaking load.

During manufacture, the suspension strand is laid up parallel to the core and the whole is then enclosed within a black polythene sheath to give a figure of eight cross section - see Fig. 1.

5. Conditions of use
Aerial cables with integral suspension strand may be erected on new pole routes constructed in accordance with F 1102, or on existing pole routes strengthened as required in accordance with F 1101.

If the cable is used in the vicinity of power circuits, the requirements shown in Protection, Power, D 0016, D 0018, D 0019, D 0020, E 0011 and E 0020, must be observed. If used at railway crossings see F 3135.

Aerial cable with integral suspension strand should not be used for the replacement of odd lengths of other types of aerial cable, because of the differing tension requirements.

6. Fittings used with Cable

Grips, Wire, Suspension
A range of multi-stranded galvanised steel grip-type fittings are available for terminating the suspension strands. The inside surfaces of the grips are sprayed with an oxide grit to ensure adequate holding power. The general form of the grips is shown in Fig. 2.

Grips, Wire, Suspension No. 1 are used to terminate 1/12 suspension strand and Grips, Wire, Suspension No. 2 are used to terminate 7/26 suspension strand.

If it is required to fit an Insulator, No. 2 in the suspension strand, a Grips, Wire Suspension No. 3 is used to secure a 1/12 strand to the insulator and a Grips, Wire Suspension No. 4 is used to secure a 7/16 strand to the insulator.

The insulator is secured to the pole using a Grips, Insulator, Pole No. 1 with a suitable length of 7/14 suspension wire, for both 1/12 and 7/16 strands.

Grips, Wire, Suspension, No. 1 and No. 2, Grips, Stay, Pole, No. 1 and Grips, Insulator, Pole No. 1, are supplied complete with "O" Clips. The "O" Clip is provided to prevent the free end of the suspension wire unwinding from out of the grip during the fitting operation or when the grip is subjected to high shock load.

Hooks, Aerial Cable, No. 1
This is used for supporting the cable at through positions with pull-on-pole up to 30ft. It is manufactured from a 'D' section steel bar and is coated with nylon containing a molybdenum additive to reduce surface friction. See Figure 3.

Plates, Wall No. 4
This is used in conjunction with Grips, Wire Suspension No. 4 when securing cables with 7/18 suspension strands to walls and buildings - F 3126 refers. See Figure 4.

Plates, Wall, No. 5
This is used in conjunction with Grips, Wire Suspension No. 3 when securing cables with 1/12 suspension strands to walls and buildings. See figure 5.

Superseded Items
In view of the large quantities in situ, the following details of superseded fittings are given. For illustrations see Fig. 6.
Clamps, Suspension Wire No. 1 - used when terminating 7/16 strand.
Clamps, Suspension Wire No. 5 - used when terminating 1/12 strand.
Plates, Pole - used to protect pole at termination but not now fitted when terminating 1/12 or 7/16 suspension strand. Used for larger strands only.
Bolt No. 31, Shackle Aerial Cable No. 2, and Support Aerial Cable No. 4 - were used in conjunction at through positions with pull-on-pole of 5-30ft.
Bracket No. 30 - used at through positions on 7/16 strands where pull-on-pole was 5ft. or less.
Support, Aerial Cable, No. 1 - used at through positions on 1/12 strands where pull-on-pole was 5 ft. or less.

FIG. 1A
 

FIG. 1B
 

FIG. 2
 

FIG. 3
 

FIG. 4
 

FIG. 5
 

FIG. 6A
 

FIG. 6B
 

FIG. 6C
 

FIG. 6D

PO ENGINEERING INSTRUCTIONS
LINES
OVERHEAD
F 1053
Issue 1, 27.6.68

OVERHEAD DISTRIBUTION
Couplings, Aerial, Cable - Description and Conditions of Use

1. General
This Instruction describes the constructional features and conditions of use of Couplings, Aerial, Cable. For instructions on fitting the coupling and jointing the intercepted pairs see P 3053.

2. Description
The coupling is essentially a split sleeve with rubber end plugs, through which the cables and dropwires enter the joint.
The two semi-circular sections of black polythene enclose the joint and are held together by means of Strips, Binding, (see Underground, A 3005). The longer section is fitted uppermost to shed rainwater.

The rubber end plugs are bolted, one to each end of a metal spacing bar, and are positioned between locating ridges on the inside surface of the sleeve sections. Each plug has a split hole for receiving the aerial cable to be intercepted and also two small holes which will accommodate all sizes of dropwire. In the case of Couplings, Aerial, Cable, No. 1, the plugs have an additional hole through which a small polythene spur cable may enter the joint. There is a thin membrane of rubber on the inside end of each plug which has the effect of reducing the size of all the holes and provides a partial water barrier. The rubber plugs are supplied complete with ebonite stops which seal the unoccupied holes when the coupling is fitted.

The metal spacing bar is also used as a mounting plate for Connectors, Dropwire (see F 1051), using Screws, 6BA X 2in.Csk. Hd. Br.Ni..P. The connectors are fitted as required without a cover and are used for the following purposes:-

1. As a connexion between intercepted cable pairs and dropwires.
    

2. For securing the back ends of intercepted cable pairs.

NOTE:- Connectors, Dropwire and the fixing screw are not supplied with Couplings, Aerial, Cable - additional requisitions are required.

FIG. 1
COUPLINGS, AERIAL, CABLE, No. 1

3. Sizes
There are two sizes of Couplings, Aerial, Cable, as follows:-

1. Couplings, Aerial, Cable No. 1 (see Fig. 1)
   This is the larger size of coupling and is for use as in par. 4 (a) on aerial cables up to 0.95in. external diameter. Up to four dropwires may be taken into the joint. This coupling is also for use as in par. 4 (b) and/or par. 4 (c) and will take a spur cable up to 0.5in. external diameter. The spacing bar will accommodate up to eight Connectors, Dropwire.
    

2. Couplings, Aerial, Cable, No. 2 (see Fig. 2)
   This coupling is for use as in par. 4 (a) on aerial cables up to 0.5in. external diameter, and two dropwires may be taken into the joint. The spacing bar will accommodate up to four Connectors, Dropwire.

NOTE:- Each of the rubber end plugs supplied with Couplings, Aerial, Cable No. 2 will accommodate two dropwires. Exceptionally, all four of the dropwire entry holes can be used. In such cases however, it is necessary to secure the back ends of the intercepted cable pairs to the main core of the cable and the coupling must be replaced by a Couplings, Aerial, Cable, No. 1 as soon as possible.

FIG. 2
COUPLINGS, AERIAL, CABLE, No. 2

4. Conditions of use
Couplings, Aerial, Cable, are for use on plastic sheathed, plastic insulated, self-supporting combined (or lashed) aerial cables when it is required to intercept pairs at through positions for the following purposes:-

1. Use of an aerial cable as a continuous D.P. - see General, D 1020.

2. Connexion of a spur cable to the main aerial route.

3. Connexion of a spur cable to provide a new D.P.

The couplings must not be used for other types of joint, e.g. joints between adjacent lengths of cable, joints between aerial and underground cable.

If it is required to intercept pairs at the first pole on an aerial route, the pairs should be extended from the joint with the underground cable and terminated on a block terminal.

COUPLINGS, AERIAL, CABLE, No. 1
Broken down into component parts

PO ENGINEERING INSTRUCTIONS
LINES
OVERHEAD
F3053
Issue 1, 1.7.68

OVERHEAD DISTRIBUTION
Couplings, Aerial, Cable - Method of Fitting

1. General
This Instruction describes the method of fitting Couplings, Aerial, Cable No. 1 and No. 2, at through positions on aerial cable routes, and the method of jointing the intercepted pairs.

For details of constructional features and conditions of use of the couplings see F 1053.

For list of tools required see TOOLS & TRANSPORT, General, A 0040.

2. Safety
Special attention is drawn to the following Instructions:-
External works in the vicinity of power circuits - J1201
General precautions against accidents - J1001
Safety guide - RG41
Poles, general test - C5101
Work on poles which carry power conductors - J1202
Work in public streets - Underground J1150

3. Preliminary work
Erect, tension, and terminate, dropwire or spur cable as required. If a new D.P. is to be provided, fit the block terminal and secure the feed cable to the pole. Allow sufficient dropwire or spur cable for jointing in the coupling.

If Connectors, Dropwire, are to be used, fit these to the spacing bar inside the coupling before climbing the pole - ensure that the rubber end plugs are bolted to the spacing bar with the rubber membrane on the inside. Prepare Strips, Binding using Shears, Hand, Tinman's, 10in; three lengths each 17½in. long are required for Couplings, Aerial, Cable, No. 1 and two lengths each 16 in. long for Couplings, Aerial, Cable, No. 2.

4. Position of the coupling
Couplings, Aerial, Cable, should be fitted within easy working reach of the pole and should normally be placed on the exchange side of the pole.

5. Preparation for jointing
If the coupling is to be used on self-supporting combined aerial cable it will first be necessary to separate the cable from the suspension strand. Commencing at about 1ft. from the pole, cut the web for a length of 15in. when fitting Couplings, Aerial, Cable, No. 1, and for a length of 12in. when fitting Couplings, Aerial, Cable, No. 2. Using Saws, Pad, Handle, with Blades, Springback, extending for about 3½in., cut the web by working the tip of the blade to and fro until the blade cuts through the web. With short, slow, sawing strokes, cut the web over the required length. Take care not to damage the cable or suspension strand.

Remove the cable sheath where the coupling is to be fitted, using Strippers, Cable, Sheath, No. 3 and Knife, Pocket, No. 2. Take care not to damage the conductors. Remove 7½in. of sheath if fitting Couplings, Aerial, Cable, No. 1 and 4¼in. if fitting Couplings, Aerial, Cable, No. 2.

Trim the surplus web material remaining on the sheath in order to ensure a good circular fit at the entry hole.

Using the slit entry hole, position the rubber end plugs and spacing bar on the cable.

Take any dropwires through the small stepped holes, the first two dropwires entering the coupling from the pole side. Spur cable is taken through the subsidiary cable hole from the pole side. It will be necessary to ease the dropwires and spur cable through the membrane on the rubber end plugs. The membrane must not be removed.

NOTE:- If using the coupling on lashed polythene aerial cable, temporarily secure the lashing wire beyond the position of the coupling before releasing the lashing wire at the suspension clamp.

6. Jointing the cable conductors
To keep the cable and suspension strand apart two wedges may be used; the small ebonite stops supplied with the coupling may be used for this purpose.

When connecting a spur cable to the main aerial cable, joint the pairs in accordance with Underground, F 3232. Waterproofed connexions are not required. Position the bank of sleeves above the spacing bar. (see Fig. 1).

FIG. 1

7. Connecting dropwires to cable pairs
The connexions between dropwires and intercepted cable pairs are made using Connectors, Dropwire. These are fitted, as required, to the spacing bar. To ensure the best arrangement inside the coupling, the connectors should be wired up as follows:-

Couplings, Aerial, Cable, No. 1 (see Fig. 1)

Number the Connectors, Dropwire, 1 - 8, commencing at the end remote from the pole, and proceed as indicated in Table 1:-

TABLE 1

Couplings, Aerial, Cable, No. 2
Number the Connectors, Dropwire, 1 - 4, commencing at the end remote from the pole, and proceed as indicated in Table 2:-

TABLE 2

When using Connectors, Dropwire, it is not necessary to strip the insulation off the cable or dropwire conductors except when terminating Cable, Dropwiring, No. 4. Electrical contact is obtained when the terminal screw is tightened on the conductor.

8. Closing the coupling
Leave the ebonite stops in the unoccupied holes in the rubber end plugs but not pushed through the membrane.

Close the coupling with the longer P.V.C. section placed uppermost between the cable and the suspension strand, making sure that the rubber end plugs are correctly positioned between the locating ridges on the inside surfaces of the P.V.C. sections. Temporarily fasten the two halves of the coupling together and then complete the closure by fitting Strips Binding, in the locating ridges on the outside surfaces of the sections, see Underground, A 3005.

9. Binding in (see Fig. 2)
Using Wire, Binding, P.V.C., bind the coupling to the suspension strand and bind the cable to the suspension strand at each end of the split in the web. At each binding use three turns of binding wire, the ends of which should be stripped and twisted together for 4ins., then cut and turned over. Do not bind dropwires or spur cables to the main cable.

Using Tape, Plastic, Adhesive, 1/2in. Black, tape the dropwires and spur cable to the main aerial cable at 3in. and 6in. from the end of the coupling.

For lashed cables, restore the lashing wire to the suspension clamp.

FIG. 2

Last revised: March 30, 2023