Kitz Forum
Broadband Related => Telephony Wiring + Equipment => Topic started by: digitalnemesis on August 12, 2016, 03:00:30 PM
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What would happen if you short circuit a telephone line for a few seconds?
Reason I ask is I accidentally short circuited a phone jack (saw sparks) and this someone cured my HR fault. :lol: (SNRM no longer drops when phone is off the hook)
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I've accidentally done this. No one came round to arrest me. I'm assuming that there's current limiting in the exchange or in the cab, some sort of short-circuit protection.
Faults of this ilk happen all the time, I believe. Last spring I had a couple of faults - nothing to do with _me_ - which were possibly of this type in the line and in the exchange hardware.
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What would happen if you short circuit a telephone line for a few seconds?
Reason I ask is I accidentally short circuited a phone jack (saw sparks) and this someone cured my HR fault. :lol: (SNRM no longer drops when phone is off the hook)
All a short-circuit will achieve is to present an engaged tone to anybody ringing your landline number ............. nothing more. Can't explain how this would 'cure' a HR.
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All a short-circuit will achieve is to present an engaged tone to anybody ringing your landline number ............. nothing more. Can't explain how this would 'cure' a HR.
Isn't a short circuit similar to applying a wetting current? Perhaps this sudden extra flow of electricity is enough to 'burn' through the oxidation on bad joints?
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A wetting current doesn't necessarily _fix_ a problem for good. It may merely move things out of the most non-linear region, away from the origin (zero volts, zero amps).
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Isn't a short circuit similar to applying a wetting current?
Only as much as using the phone.
Line current is limited, such that whether you're using the phone in your house, or you put a short on at the exchange frame, it's 40mA.
If you've got a milliammeter - try it and see.
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I very much doubt sparks were seen.
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I very much doubt sparks were seen.
I saw it with my own eyes, poked a telephone jack (test socket) with a screwdriver and saw sparks.
Can record a video if you want proof but I don't really want to try that again.
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I can personally confirm that you can get sparks. ;D
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You can actually ....... not as big as throwing a spanner across a 6" solid copper bus-bar ........ but likkle-ikkle sparks.
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I guess if you're right on top of the exchange. There's not a lot of electric left by the time you get to my house!! ;D ;D
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I guess if you're right on top of the exchange. There's not a lot of electric left by the time you get to my house!! ;D ;D
My cab is ~650m away whereas my nearest exchange is ~2km away. :lol:
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Quite a while ago, I recall discussing with 4C the maximum current that could be drawn on a telephony circuit. As I have forgotten the result I then obtained, the experiment was repeated --
[attachment deleted by admin]
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Quite a while ago, I recall discussing with 4C the maximum current that could be drawn on a telephony circuit. As I have forgotten the result I then obtained, the experiment was repeated --
Where did you source the cable which plugs into the BT socket?
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It's a MA1/631A test adaptor (also known as an Adaptor Test 3A) [1] and I believe I purchased it from JMW Limited along with a MA2/RJ45 test adaptor plus one other adaptor. The manufacturer's name is Chesivale Electronics [3] and a Google search may help.
Attached, below, are images of the three purchased and one home-made adaptor, along with part of a data sheet.
[1] http://www.telecomsupplyline.com/catalogue/testeq.htm
[2] http://www.jmwlimited.co.uk/Telecom_I_S.html?d=llinesman
[3] http://cpc.farnell.com/webapp/wcs/stores/servlet/Search?sf=&catalogId=15002&showResults=true&mf=101321&langId=69&storeId=10180
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Thanks for that, what would be the safest way to 'load' a telephone line instead of shorting both wires?
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At my previous property I used a 15k resistor to give 2 or 3mA of wetting current.
It was on the telephony side of the filter, and had no adverse effect on phone or BB.
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At my previous property I used a 15k resistor to give 2 or 3mA of wetting current.
It was on the telephony side of the filter, and had no adverse effect on phone or BB.
Is there something I could buy which does this? I'm not comfortable with connecting resistors, etc.
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Memory's not what it was, but I found this Usenet thread (http://www.broadbandbanter.com/showthread.php?t=29287) from 2010, where I was posting as '198kHz'.
As I recall, I ended up using 18kohms. I'm not aware of any commercial item, but I've got the bits in my junk box to knock something up for the price of the postage - please PM me if you're interested.
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Memory's not what it was, but I found this Usenet thread (http://www.broadbandbanter.com/showthread.php?t=29287) from 2010, where I was posting as '198kHz'.
As I recall, I ended up using 18kohms. I'm not aware of any commercial item, but I've got the bits in my junk box to knock something up for the price of the postage - please PM me if you're interested.
How much for postage and do you have a picture of how it all looks and connects?
Cheers
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The basic premise is that one needs 18kohms across the A & B wires, on the telephony side of a filter. It needs to be easily removable; if a fault is reported, I don't think a BTOR technician would appreciate chasing 18k of 'low insulation' that turned out to be in your house. ;)
I could fabricate this thing from an RJ11 adaptor, or a rat's tail ADSL filter - it all rather depends on your set up.
I gather from previous posts that you have a central filter on the master socket. Do you have any extension sockets, and if so, is there a 'spare' one with no phone.
If there is a spare extension socket, the adaptor option would be the neatest solution. Alternatively, it would mean a socket doubler (I have a spare one) feeding the phone and modified filter.
The first option would go as 'large letter' - first class 96p or second 75p.
Second one would be 'small parcel' at 5 first or 5 second.
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The basic premise is that one needs 18kohms across the A & B wires, on the telephony side of a filter. It needs to be easily removable; if a fault is reported, I don't think a BTOR technician would appreciate chasing 18k of 'low insulation' that turned out to be in your house. ;)
I could fabricate this thing from an RJ11 adaptor, or a rat's tail ADSL filter - it all rather depends on your set up.
I gather from previous posts that you have a central filter on the master socket. Do you have any extension sockets, and if so, is there a 'spare' one with no phone.
If there is a spare extension socket, the adaptor option would be the neatest solution. Alternatively, it would mean a socket doubler (I have a spare one) feeding the phone and modified filter.
The first option would go as 'large letter' - first class 96p or second 75p.
Second one would be 'small parcel' at 5 first or 5 second.
I have a NTE5A master socket and MK1 faceplate. From this I have a plug in extension to another room (nothing connected, just there in case) and a socket doubler feeding two telephones (1 corded, 1 DECT).
Which option do you think is best? Ideally I'd like this at the master socket. Would it work with a modified rat's tail filter connected to the MK1 faceplate?
Kind regards
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Which option do you think is best?
If you mean where would it work best - no difference.
Ideally I'd like this at the master socket. Would it work with a modified rat's tail filter connected to the MK1 faceplate?
Yes.
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If you mean where would it work best - no difference.
Yes.
Sounds good, can you please clarify again what I will get with option 1 and 2?
Option 1:
RJ11 adapter.
How exactly does the RJ11 adapter look like?
Option 2:
Socket doubler + modified filter
Is the socket doubler rat's tail?
I have limited clearance due to close proximity to a cupboard
Also, do you accept bank transfer or PayPal?
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PM sent.
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PM sent.
PM sent!
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Did you get my PM?
Thanks
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Sorry to jump on this thread, but suppose I fitted one of these faceplates as discussed elsewhere ...
(https://forum.kitz.co.uk/proxy.php?request=http%3A%2F%2Faa.net.uk%2Fi%2Fi%2Fnonfilter-small.png&hash=1d208f9da2fdaad727cd7d0e24cd466827496c2f)
Could the resistor be fitted across the appropriate pair on the back of that socket?
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Sorry to jump on this thread, but suppose I fitted one of these faceplates as discussed elsewhere ...
(https://forum.kitz.co.uk/proxy.php?request=http%3A%2F%2Faa.net.uk%2Fi%2Fi%2Fnonfilter-small.png&hash=1d208f9da2fdaad727cd7d0e24cd466827496c2f)
Could the resistor be fitted across the appropriate pair on the back of that socket?
No. :no: In the text accompanying that image there is the sentence --
Faceplate does not have extension wiring connections or telephone socket.
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Did you get my PM?
Thanks
Aye, I'll get back to you ASAP.
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No. :no: In the text accompanying that image there is the sentence --
My thoughts were that because the pair connects directly to that RJ11 socket, that it would electrically be exactly the same as if it were a telephone socket. Is that not the case?
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It is actually an RJ45 socket and you are perfectly correct -- that face-plate is just an adaptor, BT 600-series plug to RJ45 socket.
However if you fit one of those face-plates, I presume you would use that socket to plug in the patch lead to connect the modem (or modem/router). In that case, how would you propose to connect the resistive shunt?
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You have funds!
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However if you fit one of those face-plates, I presume you would use that socket to plug in the patch lead to connect the modem (or modem/router). In that case, how would you propose to connect the resistive shunt?
I don't have one to hand to examine, but I was assuming they would be similar to the BT part with a PCB in the back linking conductors from the plug to the socket, if so then that would be where to solder the resistor.
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I don't have one to hand to examine, but I was assuming they would be similar to the BT part with a PCB in the back linking conductors from the plug to the socket, if so then that would be where to solder the resistor.
Ah, in that case then "yes"! :)
Originally I had no idea that you intended to take the face-plate apart and presumed you were hoping for IDCs on its reverse . . .
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When a resistor is on the line, what happens when a call is received? Does the resistor lower the incoming voltage/current?
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It will have a miniscule 'shunting' effect on telephony, which will not be discernible.
It might perhaps have an effect on ADSL by causing impedance mismatch if on the line side of the filtering, which is why I recommend fitting on the telephony side of a filter - but maybe I'm being over cautious.
Some of our resident gurus may be able to throw more light on the matter.