Infinity installation -cabling question.

I'm having infinity 2 installed shortly and have just run a CAT5 cable under the house from the BT master socket into another room.

There is no power points anywhere near the master socket.
Will this cable be of any use?

Currently I've terminated it with RJ45 plugs, will they be suitable or would I need RJ11?

If i need RJ11 what pinouts will it need.

Thanks

RJ11, pins 3&4 on a single twisted pair, that's all

In reply to a post by izools:

RJ11, pins 3&4 on a single twisted pair, that's all

Thanks shame it's not RJ45 !! I'll have to buy some RJ11 plugs !

In reply to a post by izools:

RJ11, pins 3&4 on a single twisted pair, that's all

Should also have asked is the RJ11 4 pin or 6 pin ?

Actually with the old faceplates, an RJ45 with the middle two pins wired on a pair (which is usual for Ethernet) will be fine.

Not sure if this is the case with the interstitial filter, don't have one to try. The modem end though is VERY VERY likely to be just an RJ11 socket.

Yes and no!

Keep the master where it is and have the VDSL filter installed there. Use one pair of the Cat5e for the VDSL signal and another pair (plus one for the ring wire if you need it) to take the signals to your required location.

Get a modular faceplate with a BT phone socket and an RJ11 socket at the final location and connect the Cat5e to those. You can the plug your phone in there, as well as where the master is and use a short RJ11 to RJ11 lead from socket to modem.

You might or might not get the BT tech to do it for you - but if not you will need a power extension lead to the hallway as a temporary measure whilst he does the install.

Don't try to fit RJ11s to four pair Cat5e it is near impossible and also infrastructure cable is not designed for termination in plug connectors but for IDCs.

Thanks

My current BT master socket has a telephone extension cable wired from it to my dining room. I plan to leave that in place as it works. ( unless advised not to )

I thought I needed one pair either from the socket (RJ45 / RJ11 not sure which) or from the internal IDC. If that is the case and I use one pair from inside the faceplate do I just terminate an RJ11 on the same pair of wires ? using which pins ?

Go from the internal IDC - that is why it is there. You can take teh telephony too, if you want. With teh existing extension, that can remain but it does mean you will need the filter at the master.

Don't use an RJ11 plug but as I suggest an RJ11 socket and then a short patch lead. It will be either 3&4 or 2&5 - some modems are auto sensing and will detect which pair to use.

Standard Cat5e cable is solid core and designed for use in IDCs but trying to terminate it in an RJ45/11/12/14 plug can be hit and miss with some connections either not making or being less than perfect. Patch lead is multi-stranded and ideal for the blade cutting in that an RJ plug uses whereas it is possible to insert a patch lead wire into an IDC and get no connection whatsoever.

Would this work OK :

RJ45 --- RJ11
Pin 3 -> Pin2 Green / White
Pin 4 -> Pin3 Blue
Pin 5 -> Pin4 Blue / White
Pin 6 -> Pin5 Green

There's a basic guide linked to in my signature, take a look at that it may well help.

It pictures of my setup when I had ADSL, when FTTC was installed I got them to move the master socket.

Could you run 12v power over a spare pair in the cat5? (draw, length and gauge permitting)

cheers, a

Power over Ethernet (PoE) standards seem to be more like 44-50 volts. If you wanted to supply 12V, I imagine it would be possible.

I wonder why such a high voltage? Perhaps because they need the current to be low? Perhaps because it is congruent with the standard Telco power of -50V?

The higher the supply voltage, the lower the wire loss. There are several online wire loss calculators. Most are US-based with imperial measurements just to complicate

This wire loss calculator is nice though. All the maths is done in Javascript:

http://www.nooutage.com/vdrop.htm

It only goes down to 14AWG, but the values can be extrapolated to fit the common gauges of comms cables (24AWG and 26AWG).

Good quality cat5/5e cable has a conductor diameter of 0.500mm (about the same as 24AWG). And 24AWG solid copper apparently has a DC resistance of 5 ohms/100metre at 25degC. Whereas 26AWG (0.400mm diameter copper core) apparently has a DC resistance of 8 ohm/100m at 25degC. The DCRs for solid aluminium 24AWG and 26AWG are given as 9 ohms/100m and 14 ohms/100m respectively (at 25degC).

The load of the Huawei HG612 is roughly 600mA @ 12vDC.

According to that calculator, if a spare pair from a 30 metre length of solid copper AWG24 (cat5) cable is used to power the Huawei, there will be a voltage drop of 13% (down to 10.4 volts) at the modem.

And the higher the load, or the longer the cable run, or the finer the wire gauge, the worse that voltage drop will become.

The alternative VDSL2 modem from Openreach, the ECI B-FOCuS, draws a higher current of some 700mA. Powered over a spare pair in the same 30m length of 24AWG cat5 cable, that would see an even higher voltage drop of ~15%.

At some point, when that wire loss gets too great, the voltage regulator in the modem is going to give up and it will fail to energise the device.

Using a 'spare pair' in a cat5 cable to directly supply 12 volts DC to power an average DSL CPE looks to be limited to domestic cable runs of ~20 metres. Though if there's a second unused pair in the cable for 'doubling up' to carry DC power, then the effective maximum length could be doubled too.

It wouldn't be hard or expensive to do this quite tidily using standard LJ6C modules. An off-the-shelf module for RJ45. And the DC power socket could be fashioned out of a module blanking plate and a standard barrel-type chassis socket like this:

http://www4.picturepush.com/photo/a/10514432/img/pow...

Caution! All back of envelope stuff, not to be relied upon!

cheers, a

Basically true but over a short distance the loss is insignificant and can be ignored.

It does become importent with power at high currents hence the use of very high voltages on the National grid. It is partly as well down to needing to keep the weight down for overhead lines so they tend to use Ali which is not the best conductor