Telephone systems

[Paul]

Come a major event, the one thing that may keep going is the phone system. Well at least for a while.
Problem is how to access it if all you've got is a telegraph pole with wires on it or a locked building / house with a wire going into it?

CAUTION.
This thread details a way to connect to the telephone system which would be illegal.
This is for information only.

The UK and US telephone system is basically a two wire system. It's dead easy to spline into this in an emergency. Between you and an exchange a telephone essentially runs off two wires.
The 'A' wire and the 'B' Wire.

The 'A' wire sits at Zero Volts to Earth
The 'B' wire sits at -50 volts DC to Earth

There are generally 4 types of drop cables from the pole into a building.

Colour code
The first colour is wire 'A', the second wire 'B'

CW 1406 (No.12)
Pair 1: Orange/White

CW 1411 (No.10B)
Pair 1: Orange/White
Pair 2: Green/Black

CW 1417 (CAD55M)
Pair 1: Orange/White
Pair 2: Red/Grey
Pair 3: Blue/Brown
Pair 4: Green/Black

CW 1378 (No.10)
Pair 1: Orange/White
Pair 2: Green/Black

Between poles and underground systems, cables are normally thicker with more pairs. I'm not going to list them all as they can exceed 100 pairs so concentrate on wires going into a building rather than these main connecting wires.

Each pair is twisted together even on the above cables so if all else fails, pick the wires twisted together in pairs. It's important NOT to mix wires from individual pairs.

For domestic and single line installations, two pairs is normal with
Pair 1 being Orange / White and
Pair 2 Green / Black as a standby.

Again remember that each pair is twisted together.

Interesting information but useless without a simple telephone.
To make a simple service handset.
Buy a cheapy wall mounted telephone (Average price £8) and two small insulated crocodile clips.
Look at the BT plug.
The desired wires go to pin 2 and 5 i.e.
123456
Pin 1 is the opposite side the locking tab.

You'll see one of these colour codes.
Old Wiring YGBR
You need the YELLOW and RED

New Wiring KRGY
You need the BLACK and YELLOW

US Wiring RG
You need the RED and GREEN

Alt Wiring KY
you need the BLACK and YELLOW

Y=Yellow, G=Green
B=Blue, R=Red
K=Black.

Take the plug off and peel back the insulation by 3" and attach the clips as listed.
Then all you need to do outside is to strip back the drop wire and connect to
1st pair i.e. Orange and White.
If it doesn't work, use the 2nd pair Green and Black.
If no joy, move onto the 3rd and 4th Pair as specified above.

You will hear the dial tone when you've got the correct pair but don't keep hold of the wires with your fingers. If someone calls, you'll get a shock of about 75 volts AC. That stings a bit and if you are up a pole might be enough to cause you to lose grip.

Once connected, you can use the phone as normal BUT incoming calls won't "Ring".
That's because the master socket in the house filters the ringing tone onto a different pin i.e. Pin 3 of your BT plug.
There again you'd only be interested in calling someone for help not receiving calls.

As for OPSEC.

The home owner (if present) may hear a ping or two as you play about and if they pick up the phone when you are talking, they will hear you and I'm pretty certain they will want to say something to you.

That's it except to repeat :

It is illegal to hook up directly to the phone lines outside a building even if it's your own.
All information is available on the Internet if you wish to research this further.
This article is for information purposes only