Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[setecio]

Hello. What a great informative site this is! Thanks for it.

I'm currently reading about RJ11 wiring and have been unable to solve a question that has arisen. Only 2 wires of the telephone line are needed for adsl. I have recently looked at some RJ11 to RJ11 adsl modem cables (that link the microfilter to the asl modem) and discovered that most are straight through (pin 3 to pin3, pin 4 to pin 4) but some are reversed (pin 3 to pin 4, pin 4 to pin 3). This 'reverses the polarity' and I've read that UK telephone equipment can deal with this.

My question is ..... can adsl modems deal with it? .... are adsl modems designed to work no matter which way around the wires are .... and if so, are there some modems that can't deal with it ? or is it imperative for adsl modems, that the wires don't get swapped ? 

Thanks.

[jabns]

What i would do is buy some RJ11 to RJ11 cable and use a cheap usb modem like the speedtouch 330(Most people have millions of these as it all ISPs used to ship).

What to do:

*Cut cable in half
*Strip about 1inch of each end
*try 3-3 + 4-4(just twist the wires or use crocodile clips if you have any)
*try 3-4 + 4-3

Testing speed and stability on each test.

This would be a very good,safe and cheap experiment to try(i would but my HTTP and SMTP servers have to stay up otherwise i will have sore ears tommorow LOL)

****Telephone lines can only provide a small shock and you can relax your muscles and let go(I would still unplug it from the wall socket first LOL)

EDIT: I personally use 2x2(2 sets of two twisted wires) from a CAT6 cable in a 3-3 + 4-4 config.

James Barlow

[setecio]

Yes indeed, but that would only prove that the speedtouch 330 can or can't handle both.

I'm wondering about all of them and if reversed polarity on the adsl RJ11 cable could be a cause of adsl problems.

There can be 3 possible outcomes for a particular modem :
1) It doesn't matter and has no effect
2) It stops the adsl signal completely
3) Somewhere in between ... ie it degrades the signal / speed.

and then for modems in general:
1) It doesn't matter as they all have to de designed to cope equally well with both
2) It varies from modem to modem ... it which case it would generally be important to use the correct cable config.

If anyone knows if all modems for the uk have to be designed to deal with this issue, then it doesn't matter.

As I have both 3-3 4-4 and 3-4 4-3 cables, I will try both them at the weekend on a speedtouch 330.

If you google 'rj11 voice reversed' you can see alot of rj11 cable sold as 'reversed polarity for voice', so I'm trying to grasp the effects, if any, of reversed polarity on adsl modems/adsl signal.

[mr_chris]

Not something I've ever come across, or even thought to try... if you do try it, please report your findings back here! That would be great

[setecio]

Well the speedtouch 330 I tested was supplied with a 3-4.4-3 cable, and trying a 3-3, 4-4 cable made no difference in the bbmax speedtest, both gave results of 1888kbps on a fixed 2mbps line.

[soms]

Using an RJ-11 to BT adaptor and couplers and all that to the best of my knowledge having the cable wired identically at both ends registers on a butt phone as being the correct polarity.

If you intend to make custome leads, to ensure maximum ADSL transmission/minimum interference/signal loss use twisted pair telephone cable or use a twisted pair from a reel of cat 5 in telephone sheathing (purely to fit into the RJ connector).

From observations with broadband equipment I have yet to notice a device sensitive to polarity.

Broadband will even work with only one of the wires connected.
It is not unheard of for people to have a faulty telephone line where the speech doesn't work (no dial tone and no battery) because one of the two wires is disconnected yet the broadband will operate.