Will a telephone work if plugged direct into the master socket without
Broadband is provisioned on the line.
When I try to call home there is no dial tone sound, but if the phone is
picked up conversation is clear.
Could this be a fault with a connected device? Our house phone is a bit
flakey just now (it's a 2 handset mobile jobby).
Do you mean the phone bell does not ring?
If so there is no connection to pin 3 in your 'master' socket and the
phone is not getting a ringing voltage on pin 3.
Using a microfilter will regenerate the third wire wiring from a 2-
I don't think that the filter can regenerate the ringing voltage on pin
3. It is simply 'half a diplexer', ie a 3kHz lowpass filter connected
across the phone line (pins 2 and 5). In the master socket, the ringing
line from pin 3 is created by AC coupling it to pin 5 via a capacitor.
As modern phones don't use the separate ringing wire, it can be left
disconnected and the master socket - in fact, there is some evidence
that its presence can unnecessarily unbalance the domestic phone line,
and impair the ADSL speed (although not experienced here).
The ADSL spectrum is 25kHz to 1.1MHz, but as the modem is connected
directly across the phone line (between pins 2 and 5) it gets fed with
the full incoming spectrum (both the phone signal and the ADSL signal),
and presumably has its own internal highpass filtering (25kHz and
The filter is needed to prevent anything above 3kHz passing to - and
from - the ongoing phone line. Without any filter, the phone would get
fed with the full phone plus ADSL spectrum and, depending on its design,
might not function correctly - and possibly this prevents you hearing
the dialling tone. The filter is also necessary to prevent the phone
equipment from loading the line in the ADSL spectrum - which would
impair the operation of the modem.
You may be right, but as the master socket already has the ringing
voltage take-off to pin 3, I can't see any reason why there would be any
need for an ADSL filter to repeat the exercise.
I did say that modern phones don't use the ringing wire - but you
snipped that bit.
Probably for the same reason the handsets do; the circuit design is not
UK specific. And, judging from the few I've had apart, many engineers
have spent much time designing these things no doubt with varying
reasons for their choices. Some are simple passive LP filters, others
have got all sorts of gubbins going on. There is also a school of
thought that says that having a bell wire post master socket is A Bad
Thing and can upset the broadband, so providing a splitter that
regenerates it counters that.
I believe most should do but some are incorrectly designed/manuafactured
Scroll towards the end of the article for basic filter circuits.
Treat the 5 star rating of their own products and quality based on
number of components with a pinch of salt, although I have one of their
faceplate splitters that does work well.
For the OP see also
The phone should work fine.
Some cheap phones will get interference from the ADSL.
The broadband will probably fall over when the phone is used.
If you aren't getting ringing when plugged into the master then its
probably not a master or the phone is duff.
On Thu, 25 Oct 2012 12:17:25 +0100, thescullster wrote:
Yes, behind the lower half of the faceplat there is a "test socket". Plug
a *known working* phone into there, if it doesn't work it's a BT problem.
As others have said when the phone goes off hook it'll probably kill the
broadband if there is no filter in the phone's feed.
Splitter or filter?
I don't understand this statement and how it relates to anything else. If
you don't get dial tone I'm reasonably sure that you won't be able to
make any calls from that phone.
Which phone? If you pick up a phone on a line that just happens to be
ringing but the phone is not making any sound the chances are the voice
circuit will be OK.
I take it you mean without the microfilter that is used to split the
phone and broadband connections?
Yes, the phone will work when used directly in the master socket (or the
test socket behind the screw on faceplate) but taking the phone
off-hook will cause the broadband modem/router to drop the broadband
connection so this is for test purposes only.
I assume that you hear _ring_ tone in the earpiece of the phone you are
calling from but the phone(s) at home do not ring?
Absolutely, borrow one from somewhere or get a super cheapie wired
handset from argos or similar (a tenner or so) and use it to test the
line direct in the 'test socket'. If that works then test by adding back
the removed wiring/equipment piece by piece until it stops working again
and you have found the fault! If it still doesn't work then you have a
fault in the master socket or provider's wiring and you will have to
report a fault to get that fixed. If the installation has all been wired
correctly then the act of removing the split faceplate on the master
will disconnect all internal extension wiring but be aware that someone
may have cheated and added a spur off before the master - trace wiring
to be sure.
If the line is at fault then the simplest option is just to report it as
a voice fault, "phone not ringing when called" and let them deal with
it. Good luck with Bangalore telecom.
 assuming you have one with a split faceplate, aka NTE5 eg:
(a very grubby example)
Thanks to all respondents.
I have disconnected the problem phone and will buy new in any case.
So far trial calls from mobile to land line have been fine, but I'm not
sure whether this was/is an intermittent fault.
Some years back we had a strange issue where we had to make a call from
a mobile into the land line (at least make the phone ring) before we
could make a call out! Turned out to be a dodgy external joint in a
Yes I do have an NTE5 and know that removing the faceplate will
disconnect all internal wiring (as it is all new-ish internal wiring).
So the next step will be connection direct to the test socket if there
are further issues.
On Fri, 26 Oct 2012 08:56:48 +0100, thescullster wrote:
No uncommon. Ringing is a fairly hefty voltage and reasonable amount of
current, it'll break through minor corrosion that ordinary off hook line
Some variation of that fault may have returned if you pick up the land
line phone and don't get dialtone. Do you get sidetone, can you hear
yourself in the earpiece or is it dead? Assuming a real corded phone...
One problem is that the flakey phone, which until now has been the most
commonly used device is one of these digital cordless 2 handset devices.
The ones I've used don't tend to give a dial tone when "unhooked". I
now have 2 phones connected, one powered, one not (both corded). Both
seem to give good dial tone when lifted.
So far, trial calls to the land line have been successful, so I'm hoping
that this time it's just a duff phone (or pair of), now disconnected.
According to fred, the problems I have experienced can be down to a
suspect connected device.
If that's the problem all I've got to do is get new cordless phone set
and enter all our contact names and numbers!!!
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