The Joint Box

This is an underground structure where the underground cables are joined.  They can be surface constructed or deep level manholes.  The deep level manholes are generally in the big cities and are not built much today.  This is due to the dangers of gas when working underground, the cost of construction and safety issues.

Joint boxes are used where ever a cable needs to be joined.  The GPO would pull through the longest possible length of cable to reduce the joints - this is to make the cable more reliable and the cost would be reduced.

From the Exchange to the Cabinet the joints would be though joints, but between the Cabinet or Pillar and the distribution points the joints would have a number of outgoing cables.

Foot way joint box cover being lifted.  This is the correct way, using a roller.


After lifting the cover, a gas test should take place. 
A miners lamp was lowered into the chamber to test for carbon dioxide, whilst the tester, shown above, checked for explosive gases.


Gas plumbing a joint in surface box (Picture taken 1956)


A footway joint box.  This is a rather congested joint box but it shows how the cables are joined.

This picture shows cable creepage.  This is movement due to sloping ducts or heavy traffic.
In these cases the cables would be anchored to prevent them from moving.

The picture shows how the perfect joint should be made. 
The wires are joined by crimps.  Before crimps were introduced the wires were twisted together and a paper sleeve pushed over the joint.



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Last revised: March 01, 2021