UNDERGROUND CONSTRUCTION
JOINT BOXES & MANHOLES

Cables at some point require joining together or joined to multiple cables.   This is normally done in a deep level manhole or a carriageway/footway joint box.

Deep level manholes are found in large towns and cities and normally close to the exchange.  As the cables radiate away from the exchange, the cables become less congested and the requirement for big jointing chambers is reduced with carriageway and footway joint boxes being used.

Manholes would normally be constructed by a contractor whilst joint boxes would be constructed by the GPO box builders, who had specialist vehicles for the task.  Manholes would normally be installed on roads and on trunk roads they would be close to the kerb or in the verge.

Box Building Vehicle - Tools and Transport, Vehicles B3853
Click here for the Morris FG Box Building vehicle

Manholes were not the best of places to work in.  They were dirty, badly lit, could be filled with water and contain gas.  Before entering a manhole box guards would be erected around the entrance as these were deep and could severely injure a member of the public if they fell down the hole.  Then a gas test would take place, checking for flammable gas and next would be a test for carbon monoxide using a miners lamp.

If the tests were clear a man would enter the manhole and inspect it.  If it was very dirty then a gully cleaner may be called for, but in the main an electric pump was used to clear any water found.

Carriageway and footpath joint boxes were a different matter as they were not enclosed and not that large.  Any water found was generally removed with a hand pump.

Manhole type and coding - A2C7001.
Obsolete Jointing Chambers - A2G0057.
Manhole type (as 1971) - A2G0102.
Underground Chamber construction - Educational Pamphlet 2/4

After lifting the cover, a gas test should take place.  A miners lamp was used to test for carbon dioxide, whilst the tester above tested for explosive gases.