I know that 'by-the-book' you are not supposed to interfere with the wiring on the supplier side from the master socket.
However setting aside the legals is there any technical reason why it would be bad to add an extra phone socket off the main pair using a second master socket?
There is a nice little junction box inside the flat just on the other side of the wall from where I would like the extra socket. The 'correct' route would mean a long and involved path on the customer side.
TIA
It's not a good idea. You'd be paralleling up the capacitors that make the ringer work, best bet would be to run a cable back the way from the master sockets 'client' side to where you want the new socket to be.
Yes, you will have two ringing capacitors in parallel.
If you've got a two-pair cable from that junction box to the master socket you can run a ringing wire back from the master socket using a spare wire in the second pair. Extensions don't have to be electrically downstream of the master socket, although in theory-strictly-compliant they should be connected via the pluggable faceplate on a Linebox or a plug-in adapter.
Alternatively, move the Linebox to the location of the master.
Alternatively, many electronic phones don't need the third wire for ringing.
Owain
Could you not then make the new socket the master, run a cable back to the point of the junction box, stick another junction box next to the original and run the old master as an extention?
The usual advice is that you are not really supposed to have more than one ringer capacitor on a circuit, but it *does* work. I have wired three houses with extensions using exclusively master sockets and only the pin 2&5 pair. House 1 had seven such extensions (and one master) altogether (though only six had instruments attached), house 2 had six extensions and house 3 has five extensions (at the moment, three more planned). So that's my own experience, but consider this:
I have, in the course of things, taken apart several ADSL microfilters. Not one was wired up as an extension socket. Every one of them took just two wires from the phone line, did a bit of LC filtering and then had a ringing capacitor hung across the "phone" outlet. These are all BABT approved and are designed to be plugged into every telephone socket in the house. You'd end up with an all-master installation that way.
Having said that, I did see a cunning trick performed on a BT installation once: Incoming line runs through attic. One of those little four-terminal junction boxes in the attic with separate wires running downstairs to "master" socket in the hall, and into a bedroom to a secondary socket. There was no second wire between the master socket and the secondary, so how did phones on the secondary ring? The answer is that although the two line wires effectively went directly from the JB to each of the other sockets, the third (ringer) wire was brough back up from the master using one of the unused wires in the installation cable, and thence down to the secondary. Difficult to explain, and difficult to draw in ASCII, but I'll have a go:
________ incoming ========JB========secondary ||| ||| ||| master
If you don't want to go the multiple-master route, and you don't mind fiddling with BT property, would this be a suitable solution, assuming there is a spare wire in the cable between junction box and master?
Hwyl!
M.
That's fine. BT often do it themselves. (Capacitors are not in parallel as someone else said, because you do not connect the bell wire (3) between the two master sockets.)
It only becomes a (slight) problem if you use pulse dialling and have any phones sensitive to bell tinkle, as you have lost the function of the bell wire between the two master sockets to supress bell tinkle, and you could get one phone's bell tinkling as another phone pulse dials, although it's harmless.
No reason at all, the "parallel ringing capacitors" is irrelevant if you think about what the ringing capacitor does for a few moments.
But they are in parallel as far as the exchange is concerned via the ringers. I doubt that two C's is going to create a problem with ring trip but it is a poosibilty dependant on the number of C's and the impedance of the ringers.
Yep no problem, If your doing this just connect the two wires from terminals
2 & 5 in parallel and omit the wire from terminal 3 which would normally link the bell circuit to the slave.
The capacitances are in parallel once the phone is plugged in, because the other side of the ringer is paralleled on pin 5.
2-------------------------------- | | | | === === === === | | |- - -3 omitted - - | | | | | \ \ / Ringer / \ ~ 4kR \ / / | | | | 5--------------------------------Oh, I see Peter Parry has already answered this. But as I've spent 10 s on this ASCII art I'll send anyway so my creative efforts get googled for posterity.
Owain
It's not, because A+B ringers are electrically equivalent to capacitor + bell, ie they do not pass DC.
If the capacitor is shorted then there is (a) DC on the ringing wire, which can cause some electronic phones to ring, because they are sensitive to both DC and AC on the ringing wire; (b) a DC loop across the speech pair, which will cause ring trip.
Owain
Since the ringer can alternatively be placed directly across the A+B lines (i.e. like the capacitor was shorted out as is done by phones which don't use the bell wire), it's irrelevant. The shorted out capacitor in such a phone is equivalent to an infinite number of capacitors in parallel -- i.e. it's not an issue.
Also ADSL microfilters are, in effect, mini master sockets - i.e. they usually have a 2-wire input and contain their own ringer coupling capacitor after the low-pass filter on the telephony side.
Erm, but you only have two wires (and terminals) on the *input* to the master socket.
Think about REN for a minute...The caps only isolate the ringers from DC, and ite really the phones that are in parallel, not the capacitors.
The usual advice is that you are not really supposed to have more than one ringer capacitor on a circuit, but it *does* work. I have wired three houses with extensions using exclusively master sockets and only the pin 2&5 pair. House 1 had seven such extensions (and one master) altogether (though only six had instruments attached), house 2 had six extensions and house 3 has five extensions (at the moment, three more planned). So that's my own experience, but consider this:
I have, in the course of things, taken apart several ADSL microfilters. Not one was wired up as an extension socket. Every one of them took just two wires from the phone line, did a bit of LC filtering and then had a ringing capacitor hung across the "phone" outlet. These are all BABT approved and are designed to be plugged into every telephone socket in the house. You'd end up with an all-master installation that way.
Having said that, I did see a cunning trick performed on a BT installation once: Incoming line runs through attic. One of those little four-terminal junction boxes in the attic with separate wires running downstairs to "master" socket in the hall, and into a bedroom to a secondary socket. There was no second wire between the master socket and the secondary, so how did phones on the secondary ring? The answer is that although the two line wires effectively went directly from the JB to each of the other sockets, the third (ringer) wire was brough back up from the master using one of the unused wires in the installation cable, and thence down to the secondary. Difficult to explain, and difficult to draw in ASCII, but I'll have a go:
________ incoming ========JB========secondary ||| ||| ||| master
If you don't want to go the multiple-master route, and you don't mind fiddling with BT property, would this be a suitable solution, assuming there is a spare wire in the cable between junction box and master?
Hwyl!
M.
The message from Martin Angove contains these words:
Not only can it be done, but it's the standard answer if there are more phones on a single extension than can be rung by the available ringing supply.
The late and sometimes lamented Omnicom telephone exchange had many faults, as well as many virtues, but the most tremendous thing about it was the unfailingly helpful and laid-back Welshman on the end of the helpline. He recommended using only master sockets on the extensions. The only disadvantage, of course, was that the phones didn't start ringing until the capacitors had all charged sufficiently.
With American-style internal exchanges, of course, master sockets are usually a necessity. When I replaced our internal exchange I had to buy a supply of capacitors to fit into the slave sockets around the place.
Have another look, I think you will find that a master socket has 6 terminals. The line from the exchange has only 2 wires, but from the master to each slave 3 wires are used, or 4 wires (terminal 4 was used for the earth recall) on a PABX extension, or a party line. The other terminals 1 &
6 are used on some electronic switching systems where a data pair is required.
Have another look at the post to which you are replying. Specifically, the word "*input*" !!
Yes, and??
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