Poles


The mainstay of telephone distribution in the very early days.  The pole carried most of the telephone traffic, be it locally or between towns.

To carry all the wires necessary, the early poles were very tall compared to those from the 1950's onwards.  They had to be tall to get the wires over the roof tops in towns.  Poles were originally made of wood and then galvanised metal was used during the second world war.  The galvanised poles were all replaced by the late 1970's.

Originally the wires, which were un-insulated and generally made of Copper-Cadmium,  were carried on ceramic insulators which were mounted on wooden arms and known as "open wires".  Once underground cables were introduced, the amount of external wiring decreased, due to it's fault liability, cost and plant size.  The GPO used underground distribution to the street and then terminated this cable at pole top, where the line continued overhead for a short distance.  Today, modern houses have the external cable run directly into the house and no poles are generally used.

In the late 1950's plastic drop-wire was introduced (twin copper coated steel conductors - plastic insulated cable) and these gradually replaced the older style copper open wires.  The original drop wire was held up by a sliding captive device, but this was replaced in the early 1960's by a piece of twisted wire, which the drop wire was twisted around and held in place by friction.

In the late 1970's the Post Office introduced fibreglass poles and these were installed in positions were a person may be in danger when using a pole.  i.e. pointed railings below the pole.  These poles only used drop-wire and the drop-wire was clamped, inside the pole, at the bottom.  These and the Block Terminal, which the drop-wires would be connected to, could be reached by a small trap door in the side of the pole at working height.

In the late 1980's the twin conductor, grey coloured, drop-wire was replaced by a four conductor drop-wire which was round in shape and black in colour.  The wires were copper and were surrounded by steel support wires.  Although the support wires where insulated they were not intended for electrical connection.

Poles come in different sizes and are well marked.  The marking are 10 foot from the base of the pole so expect to find them 6 foot above ground level.  These marking show the type of pole i.e. Medium, Light etc, the date of manufacture and the producer.  In the picture below you can clearly see the owners name, the 10 foot mark, Medium pole of 12 metres in length and produced in 2006.

Poles should always be tested whenever they are climbed and this is firstly a visual inspection followed by tapping around the base of the pole with a hammer and then pushing a pointed rod into the wood to see how far it will go.

Poles are buried to a depth of around 4 feet. 

There are other markings that can be found attached to poles.  In the picture below, on a pole that was seen in the Forest of Dean, the markings from top to bottom are:-

  1. Date of last official inspection.

  2. D plate, which means defective - the pole should not be climbed.  A D plate could fitted because, the pole is rotten, near dangerous railings etc.

  3. DP242 means Distribution Point No. 242, which is the terminal block at the top of the pole (this is not the pole number).

 

Pole Erection Unit
This vehicle is fitted with an auger (stowed in the picture) to drill the pole hole and a winch to put the pole into place

 
 
BACK Home page BT/GPO Telephones Search the Site Glossary of Telecom Terminology Quick Find All Telephone Systems

Last revised: June 24, 2012

FM2