Big and black

[Dr Lobster*]

this has bothered me deeply for some time, does anybody know what on earth those big black things fixed to the side of telegraph/power transmission poles are?

[Nick Harvey]

They're junction boxes, where one length of cable is joined to the next length.

Bear in mind that, in the case of telephones, there will be up to 200 individual pairs of wires in each cable and each of those wires needs to be joined to the one of the same colour combination in the next length of cable.

Did you want to know that the colour codes go blue, orange, green, brown and slate (that's grey to you and me) with a white; then the same five with a red; then with a black; then with a yellow; then with a violet? That gives a bundle of 25 pairs of wires, which then get repeated in further bundles, each with a different coloured nylon tie round them, up to the size of the cable.

Oh, and the boxes are mounted up that way to stop the rain getting in.

Oh, and the colour code is known to trainees as BOGBRuSh.

[Dr Lobster*]

Thank you Nick. When you put it like that it seems obvious what it is, but it really had me stumped.

I had thought they might be some sort of monitoring node, but even more mundane than that.

in a slightly unrelated note, I notice in the back of my BT box only two wires are actually used, the rest are folded out of the way, so are these there for 'spares' or in case i need another line put in?

[Gavin Scott]

Mr Harvey - you edited your original reply with some scintillating things there, but I hadn't looked again until the good Doctor replied.

Henceforth you shall have special dispensation to reply to your own posts in these circumstances, so that we do not miss nuggets of thy wisdom.

[Nick Harvey]

I notice in the back of my BT box only two wires are actually used, the rest are folded out of the way, so are these there for 'spares' or in case i need another line put in?

Yes they are.

If the line comes in on a 'dropwire' as it's called, the orange and the white will be used for the first line and the green and black will be folded or rolled back out of the way, ready for a second line.

Once inside the building, a junction box will connect the dropwire to internal cable. The orange will connect to the white/blue (mainly white, with blue 'stripes') and the white will connect to the blue/white (mainly blue, with white 'stripes'). Again, at this stage, the internal orange, green, brown and possibly slate pairs will be folded or rolled back out of the way.

Only after the master socket does the orange internal pair come into play, the orange/white carrying the AC ringing current which has been split from the DC speech path in the master socket.

So what else can I tell you and Gavin? The orange in the dropwire is known as the 'A Leg' and is nominally the 'earthy' leg. The white in the dropwire is the 'B Leg' and is at minus fifty volts compared to the A Leg.

[Gavin Scott]

This is all good stuff.

*scribbles notes furiously*

Does the "maximum Ring Equivalent Number" still come into play these days? I remember adding too many extensions in the house and making the bell ringer in the hall go nuts.

My current residence is a little small to concern myself with extra phones, but I wouldn't mind peppering them around my next abode, should this sale ever go through.

[Sput]

Surely you would use multiple wireless phones sharing a base station gav, you're not some luddite are you?

[Gavin Scott]

Surely you would use multiple wireless phones sharing a base station gav, you're not some luddite are you?

I have a bit of an odd penchant for American desk phones I remember from television programmes in the 1980s.



That's the style I like - and yes, I'd quite like a pink one. Next to my bath, like some big shot.

And there's something much more satisfactory, quality of sound wise, with a corded phone. I've had a couple of DECT wireless ones in the house and they're all a bit rubbish by comparison. I'm back to a corded one again.

That's why I'd like a few phone points - I'm certainly not going to be dragging extensions around my new pad.

Or I suppose I could be super smart and run my phone, data and AV off Cat6 circuits.

[Nick Harvey]

Does the "maximum Ring Equivalent Number" still come into play these days? I remember adding too many extensions in the house and making the bell ringer in the hall go nuts.

Yes, but most modern phones, with elecronic ringers, have a REN of about 0.1, so managing to get up to a total of 3 is a bit difficult unless you have pink telephones in all your rooms!

Talking of nice sounding telephones, feel free to grab this little item and download it into your mobile phone if you like it.

[Gavin Scott]

Does the "maximum Ring Equivalent Number" still come into play these days? I remember adding too many extensions in the house and making the bell ringer in the hall go nuts.

Yes, but most modern phones, with elecronic ringers, have a REN of about 0.1, so managing to get up to a total of 3 is a bit difficult unless you have pink telephones in all your rooms!

I think its pretty obvious I will!

Talking of nice sounding telephones, feel free to grab this little item and download it into your mobile phone if you like it.

Fabulous. I actually have a device from a stage manager's desk which will send a healthy enough voltage down a line to make a telephone ring. Using a multi-pole GPO switch (naturally), you can select the ring-ring British sound, or the US long single ring.

Tried to connect it for a stage production, many years ago, to a pre-1950 telephone which came out of a telephone box I think. We tried every combination of connection until we opened it up and found it didn't have any bells in it to begin with.

So we played the sound off a Revox.

Told you it was years ago