Many people remember the overhead cables and wiring that was everywhere in the mid 20th Century. This has reduced in size significantly due to technology and an eye to efficiency.
This section deals with the overhead construction which looks quite simple until one delves into it!
Overhead wiring starts at a Distribution Point, whether that be the Exchange Gantry (roof derrick/standard) or a simple 20 pair cable terminated at the top of a pole.
In the nineteenth century all the external wiring was bare open copper or iron wire. Cost was the essential criteria, but inefficiency and congestion caused the move to underground multi-wire cables. As underground cable costs dropped and more customers signed up for telephone service the underground cable network grew. Today, on a new housing estate, you will not see any cables or wires as they are fed underground straight into the building.
Even exchanges were joined together by the use of overhead wires. These used heavy duty poles and heavy gauge wire as transmission was paramount (some of the old poles can still be seen on major trunk roads). Underground copper and Co-axial cables replaced the overhead wires and these themselves where sometimes superseded by micro waves connections. Today the exchanges are connected by Fibre Optic cables and the micro wave dishes on the BT Tower are fibre glass dummies!
But back to Overhead Construction and it's complexities.
Poles - what size, loading strengths and height are required, will the copper wires droop and what happens when they are ice laden. Today poles are not that high but in the 19th Century the poles towered above the roof tops.
What metal work is required to support the wiring and how do we stop poles falling down due to weight of cables.
Move on to Aerial cables (suspended multi-core cable) and the weight rises substantially. Erection is done with a temperature gauge and dynamometer.
Today we have a number of mechanical aids to assist in overhead operations, but 100 years it was done by hand - check out the weights of the largest poles and see how they were erected!
It is actually highly complex, especially for those who had the
job of specifying construction.
Overhead construction party (1885)
Last revised: April 03, 2021