Strange ringing problem

[StephenMG]

Hi all,

Just when I thought my ringer problems were sorted (https://www.vintage-radio.net/forum/...ad.php?t=56369) it seems they're not...well not quite anyway!

The background to all this is that I moved house a couple of weeks back. The new house has a NTE5 socket and the previous occupier has added a single extension into the dining room. No other extension cabling exists. I have connected my cordless phone into the master socket and my 332 into the dining room extension.

All seemed well but over the weekend I tried calling home on my mobile a couple of times but failed to get through. When calling I heard a ringing tone a few times then silence so I wasn't sure if it was still a 'live' call (just not giving me a ring tone) or had been disconnected. I tried it again when I was at home and found that even when the ringing tone had stopped I was still able to pick up the house phone and be connected to my call from my mobile - so it was ringing, but not ringing if you see what I mean! Later my sister said she'd been trying to call me at home but each time after a couple of rings she'd been cut off and returned to the dial tone. No phones at my end ever rang while she was trying to call. The odd thing is that it's intermittent and the phone/ringing works fine at other times.

Can anyone offer any reason why this might be happening? Is it likely that my 332 is causing this problem? If there was a ringing problem in the house (such as exceeding the REN) would that cause the symptoms the callers are hearing, i.e. ringing tone stopping or being cut off after a few rings?

The only other thing I've done (about a week ago) is to install a BT I-Plate in a bid to give my broadband the best environment to work in. I understand the I-Plate works by isolating the bell wire on pin 3, so I assume it just breaks the connection on 3 between the master socket and anything plugged in to it? I also presume that my 332 still rings because it is plugged in via an ADSL filter which restores the ringing circuit on pin 3 via it's own capacitor? Have I got that right? Would any of that have any negative impact and contribute to the problems I'm seeing?

I also notice that when my cordless phone is connected directly to the test socket there is no background noise at all - it's crystal clear - yet when the extension wiring is brought back in to play there is a slight background hum and the odd crackle. I also noticed that it's been wired with flat cable not the round stuff - does that mean the 2-5 pair is not twisted? Would that account for the hum?

I've got just my cordless phone plugged into the test socket for the moment so I can see if any problems appear with that simple set up, but my knowledge doesn't extend to knowing whether it's likely to be my 332 that's causing the problem, or the extension wiring or a fault on the line itself.

If my 332 was faulty and causing the REN to be too high would it cause this problem? It's been converted (not by me so I really should check it) but the 3.3k resistor tests out OK on a multimeter.

Sorry for all the questions but this is stumping me so any suggestions would be desperately appreciated!

Thanks,
Mark

[russell_w_b]

Originally Posted by StephenMG

The only other thing I've done (about a week ago) is to install a BT I-Plate in a bid to give my broadband the best environment to work in. I understand the I-Plate works by isolating the bell wire on pin 3, so I assume it just breaks the connection on 3 between the master socket and anything plugged in to it? I also presume that my 332 still rings because it is plugged in via an ADSL filter which restores the ringing circuit on pin 3 via it's own capacitor? Have I got that right? Would any of that have any negative impact and contribute to the problems I'm seeing?

The BT plate with built-in ADSL filter will give a filtered ADSL output, and the telephone extension terminals to which extension sockets are routed will have provision for all three wires (2, 3, 5). This means that all your telephone extensions can be connected to terminals 2, 3, 5, and your filtered ADSL will still be available at the BT faceplate on the master box. You need no other ADSL filters on your system.

Compare this with individual ADSL filters: the third (bell / anti-tinkle) wire will be broken wherever a plug-in ADSL filter is located. Whilst the bells on any extensions plugged into individual ADSL filters will ring satisfactorily (as you point out, the third wire is provided 'locally' in the plug-in ADSL filter), you will get 'tinkle-bell' on other extensions when dialling, as the bell-shunting and dial spark-quenching circuitry that uses the third wire will be broken.

This is why the ADSL faceplate filter is a good thing: it allows continuity of wires 2, 3, 5 around all one's extensions, but still provides for a filtered ADSL output - albeit at the point of the BT faceplate filter.

Originally Posted by StephenMG

I also notice that when my cordless phone is connected directly to the test socket there is no background noise at all - it's crystal clear - yet when the extension wiring is brought back in to play there is a slight background hum and the odd crackle. I also noticed that it's been wired with flat cable not the round stuff - does that mean the 2-5 pair is not twisted? Would that account for the hum?

It may do, as it may pick up mains hum from adjacent cables or equipment. Better to rewire your extension socket(s) in screened cable - CAT5 will do if it isn't too bulky. Crackles indicate dodgy plug-in points or intermittent connections. The fewer joints, the better.

Originally Posted by StephenMG

If my 332 was faulty and causing the REN to be too high would it cause this problem? It's been converted (not by me so I really should check it) but the 3.3k resistor tests out OK on a multimeter.

Wouldn't have thought so: not with one 332 on the line - with or without resistor. When you converted it, you did take the internal capacitor out of circuit, didn't you? Too much capacitance (master box capacitor between pins 2, 3) in parallel with the 332s internal capacitor effectively between pins 2, 3 may resonate with the bell coils and allow an excess of current to flow causing a 'ring-trip' - although I'm not sure what 'ring-trip' is set at.

Check your 332 is converted properly and the internal capacitor is removed from circuit, and also check your extension wiring carries wires 2, 3, 5 from the terminals on the rear of your new BT faceplace filter to your extension(s), and that the wiring is connected to 2, 3, 5 there.

[StephenMG]

Originally Posted by russell_w_b

When you converted it, you did take the internal capacitor out of circuit, didn't you? Too much capacitance (master box capacitor between pins 2, 3) in parallel with the 332s internal capacitor effectively between pins 2, 3 may resonate with the bell coils and allow an excess of current to flow causing a 'ring-trip' - although I'm not sure what 'ring-trip' is set at.

This certainly sounds worth investigating. The 332 was already 'converted' when I got it so I had assumed it was done properly without actually checking. I will definately check when I get home later though as 'ring-trip' does sound like what's happening, i.e. the ringing tone stops (or doesn't get a chance to start) both for the caller and the ringing phone as if taken off-hook even though it's still on-hook.

As for the BT I-Plate, it's not actually an ADSL filter as it only has a socket for the telephone - you still have to use ADSL filters as well. I think all it does is break the ring wire 3, the thinking being that with that wire removed it will not act as an 'aerial' picking up interference that slows down your broadband. In my case I think it'll be causing more trouble than it's worth and I should ditch it and go for a full blown ADSL filtered faceplate, especially as my router is connected to the master socket anyway.

Anyway, my sincere thanks for your help. I will investigate the conversion of my 332 later and report back!

Cheers,
Mark

[Station X]

Check that the extension socket is an extension socket and not a master. An extension socket will have nothing in it except a socket ie no capacitor or other components.

Multiple master sockets are a common cause of "ring trip" which is what you describe.

[StephenMG]

Originally Posted by Station X

Check that the extension socket is an extension socket and not a master. An extension socket will have nothing in it except a socket ie no capacitor or other components.

Multiple master sockets are a common cause of "ring trip" which is what you describe.

Thanks for the advice Station X, much appreciated.

The extension is definately not a master as I had it apart last night checking the wiring. However, until I get home to check it, my money is on the bloke who converted this 332 not having removed the strap between terminals 10 and 11 leaving the ring capacitor in circuit as suggested by russell_w_b.

I assume that would have a similar effect to having another master socket in place?

[Red to black]

Hi,
FWIW I have had a faulty ADSL filter cause this problem before, ie. phone ring once and then stop, but still connected if answered, if you know what I mean.

I assume (but stand to be corrected) the additional capacitor in the filter was breaking down under load WRT the 'ring' voltage on the line.

Cheers,
Baz

[russell_w_b]

Originally Posted by StephenMG

Yes indeedy.

The equivalent impedance of the paralleled capacitors - one in the telephone and the one in the master LJU - and bell + resistor found on one telephone (fitted with a 1000R bell, like a 706 or a 332, say) equates to 4855.6Z, or 4848.4 + j264.21, and this load would attempt to draw a current of 15.45mA. Without a 3k3 resistor, the equivalent load equates to 1570 8Z (1548.4 + j264.21), attempting to draw 47.75 mA!

If four such extensions are connected (telephones in which the original capacitor has been left in circuit), there will be FIVE capacitors paralleled with FOUR bells in circuit, resulting in an equivalent impedance of 1228.4Z (1212.1 - j199.25) where a 3k3 resistor is fitted, or, worse, 435.4Z (387.4 - j199.25) with no 3k3 resistor! Respective currents of 61.05mA and 172.2mA will attempt to be drawn from a 75V RMS ringing voltage, which, of course, the supply can't provide.

These figures are based on a typical 59A bell-motor impedance of 2555.17 at a phase-angle of 52.67 degrees, or 1549.46 + j2031.76 and are rounded up. A ringing voltage of 75V RMS 25Hz is assumed.

[russell_w_b]

Originally Posted by Red to black

I assume (but stand to be corrected) the additional capacitor in the filter was breaking down under load WRT the 'ring' voltage on the line.

Could be the case, Baz. The voltage across a capacitor (be it master LJU or ISDN filter) can be as high as 123V for a 75V RMS 25Hz supply.

[StephenMG]

Well, I checked last night and the 332 appears to have been converted properly, i.e. the old ringing capacitor is no longer in circuit. I tested it all with a meter and there is definately no continuity to the capacitor.

So, bang goes that theory and back to square one!

I can't find anything wrong with the phone itself so I'm beginning to suspect the extension wiring. As I said before it does introduce a slight hum and some crackling and, tracing it's route through the house, it's entire route seems to be under carpets and, into the dining room itself, is incarcerated under laminate flooring. That makes me very suspicious that it's been damaged or is crushed somewhere.

If there was some crushing and possible damage to insulation presumably that could cause an intermittent short when the ringing voltage was applied and cause the ring trip?

I have my cordless and the 332 connected via splitter directly to the test socket at the moment and will use it like that for a while to see if the problem comes back. So far it's been fine, but then it was fine for most of the time before so time will tell!

Cheers,
Mark

[Station X]

If the extension wiring is isolated and if by splitter you mean a simple two way adaptor rather than an ADSL splitter, then I would say that the extension wiring is faulty.

Before condemning it I would check that the wriring between jacks is straight with no crossed wires.

[StephenMG]

Thanks Graham.

I've already checked the wiring in the extension and it's not crossed anywhere. I also remade the screw connections in the extension socket and pressed down the IDC connections in the master socket, although I didn't remove and repunch them because I couldn't find my #&@#$#& punch tool!

I also checked for signs of a short between each of the 4 lines with a meter but nothing showed up.

The only odd thing I did notice was a hint of 'blue' around one of the screw terminals in the extension socket which I presumed was a little corrosion. I cleaned it up but the crackle is still there.

I think I'll leave it all connected to the test socket for a week or so and if I get no problems I'll scrap and re-wire the extension.

Thanks again for your help.

Cheers,
Mark

[Tim]

although I didn't remove and repunch them because I couldn't find my #&@#$#& punch tool!

An old credit or similar plastic card makes a good "emergency" tool.