UNDERGROUND CABLE - MAIN

This cable would be run in a continuous length if possible to avoid joints.  The long distance cables would have loading coils installed at intervals along the route.

Due to it's size the cable is rather heavy, so length is sometimes restricted due to the amount of cable that can be transported on a drum and pulled through the ducts.

These cables are air pressurised, to prevent ingress of water, and as they were expensive cables, the less joints means literally no maintenance.  It was found that if the cable leaked, the pressure would generally be enough stop any water entering the cable to far  until the leak was repaired.  In reduction in air pressure would operate an alarm in the exchange.

In the early days of the Telephone, there was no such thing as multi-core cable and customers were fed with open wires directly from the exchange to the premises.  Click here for more details.

The main cables terminate at one end on the Exchange MDF and the other end in street Cabinets.

Handling these cables was also difficult due to weight and size of  some of the drums.  The big drums when full of cable could weigh up to 3 tons.

Transportation was also difficult and special cable lorries and trailers were purchased.

It would take a gang to lay the cable and this would be done by positioning the cable at a manhole, either leaving it on the carrier and supported by jacks and then pulling the cable up the duct way.  A strong rope would be used and this would be pulled by a cable winch.  The cable would be fitted with a cable grip which has an eye on the end and the rope would be tied to the eye. Click here to see what a cable grip looks like.

In the 1970's a Cable pulling vehicle was employed and this vehicle was for heavy cabling and required a 4 man crew - See A2D3160.

Cable hauling (1949)
Winch end
Note the bar wedged against the winch to prevent movement

Cable hauling (1949)
Cable end

Cable hauling (1954)
Winch end

Cable hauling (1954)
Cable end

Heavy Cabling

A large cable drum on a trailer

The cable drum has been rolled off of the trailer.
It is now being jacked up to a point where it will turn freely.

Fixing the cable grip in place.
In this case they are also adding additional binding due to the weight being pulled through.

Cable being fed down the duct.

This picture is a close up of a cable guide consisting of a row of rollers.
This device is used to ensure the cable has a free run into the duct.
This is beginning of the cable as the grip can be seen.

Last revised: April 20, 2023