Basic rj11 question

The Irish phone network wiring is very straight forward. Two wires presented on the center two pins of the RJ11 socket and the polarity is not important. All of the services PSTN and DSL don't care which way around you connect the wires.

All the other wires are spare for second lines and various obscure uses : alarms, ISDN, office phone systems, privacy loops and so on.

You can ignore them.

If there's still a phone service or even a dial tone on the line it can be easier to find which pair.

Otherwise just check what's connected to the incoming like by opening the Eir socket and see what's connected to L1 and L2

mordeith wrote: »

So any two wires to the two centre pins will do?

No. The line is only carried on two wires the other two will be dead, spare wires.

It looks like they used the blue pair (blue solid and blue and white stripe).

What you could do is buy a simple telephone socket (good quality one) and just connect the blue and white pair to the centre two contacts and then plug in a normal telephone cable between the modem and the socket.

To connect an RJ11 or RJ45 connector you need a crimping tool. They're done by just pushing the unstripped wires in and crimping them on. There are little blades in the plug that pierce the insulation.

In modern wiring the blue pair is normally the phone line.

However, sometimes it's the orange pair in older installations and in much older wiring all 4 wires had individual colours and weren't necessarily always connected the same way as they weren't intended to be user serviceable. Sometimes it's also just a grey and white twisted pair. Depends on the era of the installation and what the common type of wire that was used at the time was.

It looks to me like you've a plug that was made up by a technician. Just get a phone socket, strip back the wire a bit and connect the blue pair to the centre two terminals. It would be far easier than trying to crimp on an RJ connector if you don't have the tools.

Any simple phone socket of reasonable quality will do the job. Just make sure that you connect the wires to the terminals giving them plenty of contact with the copper and making sure none of your wires are shorting or loose - good, well fitted connection.

Then just plug a normal phone cable between the modem and the new socket.

mordeith wrote: »

When you say a twisted pair is each wire of that pair for one pin each or both wires crimped onto one pin as if they were one wire?

Just use one wire per pin but don't treat them as individual wires that can be used in any order. for example, don't use one half of the orange and blue pair.

A pair should have a circuit on it. The wires are twisted in pairs because that balances their electromagnetic fields off each other when they're opposite sides of the same circuit, preventing interference.

So if you're using blue for your line, you use the blue pair. If you're using orange you use the orange pair. You don't put one leg of the circuit on blue and the other on orange.

All you need to do is connect the blue pair to the centre two pins in the phone plug that's going into the modem. Beyond that it's all just spare wires.

mordeith wrote: »

Well I won't be trying it today. Turns out the rj11 plugs I bought are actually rj22 (despite being called rj11 on the website)

RJ11 plugs are designed for smaller diameter cable than is normally used in Ethernet cable. That is likely why the connector came off so easily when you dropped the router. It's just going to be a bodge job if you redo it.