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Device on UK telepone pole

Les Jones

Well-Known Member
Most Helpful Member
I spotted this device on a telephone pole (In the UK) I have not seen one of these before and was wondering if anyone knows what it is ? I suspect it could be some form of optical fiber to copper transition unit but it may just be a junction box.
20210129_110116.jpg

Les.
 

MacIntoshCZ

Active Member
Thats portable military fridge for astrazeneca vaccines. =)
Actually dont know what it could be
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Is it perhaps just a cable joiner? - it looks like the same cable going in the bottom and out of the top - perhaps the cable had been damaged, and that's the repair?.

The unit itself looks brand new, but the cable above and below looks old and moss covered.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
As Nigel says, a joint - a junction box, just a very ugly one!

it likely has a mass of individual scotchlok type "jelly splices" joining the individual cores between the two cable ends & the casing is for weather protection.

This is an underground one, but typical BT technique:

 

JimB

Super Moderator
Most Helpful Member
My best guess is that it is a large ferrite clamp.

Under each white clip is a split torroid core.
Closing the clip brings the two halves of the core into close tight contact to ensure an air-gap free magnetic circuit through the torroid.

Why is it there?
To attenuate electromagnetic interference into, or more likely out from, the cable.


Further research...
If you pass by the thing again, have a close look, there appears to be a name moulded into the housing, near the top.
Always good for googling.

If you are feeling adventurous, grab hold of the cable and see if you can jiggle it up and down through the unit.
If this is what I think it is, the cable will just pass straight through.

JimB

Edit:
I with that I could spell toroid correctly!
 
Last edited:

rjenkinsgb

Well-Known Member
Most Helpful Member
See the thing in this photo that has the yellow tape around it - I reckon that's the back of a similar style junction "joint" or DP (distribution point) casing, as BT call them, a waterproof junction box. You can see the latches on the smaller one to right & below it.


 

fourtytwo

Active Member
I am amazed they put it that low on the pole, looks like vandal candy to me!
I would go for the filters too but why o_O
 

rjenkinsgb

Well-Known Member
Most Helpful Member
Finally found the BT name - it's an "MJC", a Mechanical Joint Closure.

They are made to similar standards by various companies, this is a Tyco one - note the same ten sets of clasps for the cover.

And a Commscope one - I think that may be the semi-legible name across the end bars in the original photo:
 

Les Jones

Well-Known Member
Most Helpful Member
Thanks for all the replies. I think Nigel is probably correct that it has been put there to repair cable damage at that point. I was hoping that it was a new way to make the fiber to copper transition as I think my broadband speed is limited by the distance I am from the roadside box where the transition is made at the moment.

Les.
 

JimB

Super Moderator
Most Helpful Member
Finally found the BT name - it's an "MJC", a Mechanical Joint Closure.
Well done, I have learned something today.

I am amazed they put it that low on the pole,
If that is where the existing cable was damaged and had to be repaired, then that is where the MJC would be fitted.

I would go for the filters too but why
Because when RF signals, which is how broadband internet is distributed to the customers, is send along a ratsnest copper wire system like this:
1611931403311.png

Then stray RF signals will be radiated far and wide.

The filter attenuates the common mode currents caused by the unbalance twisted pair wires.

JimB
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
The datasheet says no shelf life, so you have to use it right away? They might mean indefinate shelf life.

I tried to find it too. I had no luck. Nice job finding it.
 

gophert

Well-Known Member
Most Helpful Member
Google image search says it is a section of track from a Lionel train set. Any questions?
 

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