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[LoopyJuice]

I have come across an installation that baffles me, the situation is as follows:

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Old BT socket -> extension cable -> adsl filter  -adsl socket on filter> adsl router
                                                |-phone socket on filter> another adsl filter -adsl socket on filter>cordless phone base station

In this configuration the phone works and the DSL works very well at around 6mbps which is the best it will get given exchange distance etc.

If i change the RJ-11 -> RJ-11 line on the phone to an RJ-11 -> Phone cable and plug it into the phone side of the adsl filter (doing away with the 2nd filter entirely) the phone is silent and doesn't work, have replaced the filter but same problem, its hugely weird to me that the phone only works in the adsl side of the filter... any suggestions or ideas?

Thanks

[HPsauce]

It's probably a non-standard (or just different) use of pairs in the cables between the RJ11-RJ11 and RJ11-BT cables.

I used to come across this a lot with modems, some would use the inner, others the outer pair of a 4-core flat cable.
And cables could be different at each end in the way they were wired into the plug.

If it works as it is why worry?  8)

If you really want to understand it get your multimeter out and check what is connected to what in each case. Personally I wouldn't bother. 

[BritBrat]

American plugs are wired differently, do as said above and meter them out.

I will see if I can find the link that explains it.

Just when you thought you understood it all, a brief word on plugs.  The standard plugs encountered are the small RJ11 found on line cords at the telephone or modem end and the BT431A plug at the socket end. On RJ11 it is usual for the centre two pins to carry the signal, on BT431A it is the outer two.

By a masterpiece of technical superiority between them the BSI and BT managed to number the 431A plug in the British Standard as a mirror image of the socket, so when inserted pin 1 on the plug goes to pin 6 on the socket, pin 2 to pin 5 and so on. 


wppltd.demon.co.uk

[sevenlayermuddle]

Exactly as stated by HP and BritBrat, the two cables are probably just wired differently.  Where did the two cables come from... I assume the RJ11-BT one is not the one that came with the phone?

It's also worth pointing out that the RJ11 'dsl' socket on most(/all?) microfilters isn't actually filtered at all, it just connects directly to the incoming line- pair.  So I'd say the second microfilter is just acting as a wiring adaptor to give the required continuity to the phone.    And since you have it daisy-chained off the phone-side of an earlier filter, you still get the required filtering that isolates the phone signals from the DSL so everything should probably work, if a little unconventional.

- 7LM