Cable Markers

The observant Gosportian may have spotted some unusal and intriguing metal plates during a walk down the streets of Gosport. They are to be found close to the wall of a garden or front of a building but what are these engimatic markers?

City of Portsmouth Extra High Tension Junction

Back in the nineteen thirties Gosport received its electricity supply from Portsmouth. The cables had a limited length before they required a joint and this joint was often marked with a plate such as these.

Once again I am indebted to Gosport resident Terry Rendall for giving some background information on these plates. He writes:

As you can imagine, HT steel wire armoured (SWA) cables are very dangerous, occasionally at work, we exposed or came across large unrecorded cables.  If we were unable to trace them or even if we could and had to work on them or even known cables that we had previously isolated, we still had to proceed with extreme caution and carry out a strict procedure known as spiking the cable.  This was carried out with a crude looking device which had a hole with a sharp wide steel chisel poking through it.  This device was carefully positioned on and around the cable and clamped tight.  The chisel was either struck by hand with a lump hammer, a bit nerve racking! Or you could choose to use a cartridge of a given strength determined by the size of the cable, this was loaded into a chamber with a hammer and trigger mechanism attached to the spiker tool.  A long piece of string was then attached to the trigger and operated from a distance of your choice,  in my view a much more civilised idea. 😃 Either way, the SWA, often used as earth, was partly severed or forced apart allowing the chisel point to cut deep down into the inside copper cores causing a short circuit and hopefully the substation trips to activate. You still had to carry out tests and be cautious.  Check, check, and check again.
Joints and junctions are always vulnerable points, you can’t have too many info marker plates along an underground cable route! 

I am not an industrial electrician or cable jointer, this is what I observed whilst assisting and working alongside my work colleges on joint projects, and I do not know if this is the current procedure.
I once knew a chap, a cable jointers mate, he was instructed to cut through a cable purely on visual appearance, the jointer thought it was dead, he skipped procedure, big mistake.  Turned out to be HT, later the mate told me there was a loud bang, a large bright flash, the hacksaw almost disappeared, a very small part of it was flung out of the cable pit.  He was so fortunate to have ended up with blackened face and hands, light burns to hands and clothes, and slight retina damage, an amazing escape. 
At work, we called high voltage cables high tension cables, The French ‘tension’ means voltage .

This metal marker plate, to be found close to Alverstoke Village at the end of Clayhall Lane, is shown on O.S. Maps as a Post Office Cable Marker. Thanks once more to Terry for spotting this.

Another one, in stone, can be found in Stoke Road, nestling next to the wall of the church.

General Post Office cable marker