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[tickmike]

With the new NT5E Mk3 face plate there is not bell wire so as I have said before I had to use a (untidy looking) plug-in dangly filters to get the bell to ring on my old land line phones.

Getting a phone working in my workshop I used a old Mk 1 NT5E face plate (my old master socket which OR chap left me) to get the phone to ring without a 'dangly filter' .

All other phones seem to work ok .

Is there any problem in using this method ?.

I also need to attach a larger outside bell on my workshop, so could I take the feed from this face plate ?.

[burakkucat]

It is the presence of the 1.8 microfarad capacitor (part of the RC shunt across the pair) that is providing a locally generated signal to ring the bells and not the Mk 1 SSFP. I would remove the latter and just use the basic old NTE5/A as an extension socket.

What effect does it have on the circuit? Well it is now doubly terminated with RC shunts in the Openreach NTE5/A (the master socket) and in your own extension NTE5/A.

Working from memory, the shunt consists of a 1.8 microfarad capacitor and a 470 k Ohm resistor in series. You have two shunts in parallel across the pair. It's late in the evening and I can't remember how to calculate the impedance that those paralleled shunts are placing across the pair. Perhaps Roseway or WWWombat could provide the relevant equation, please?

[sevenlayermuddle]

Getting a phone working in my workshop I used a old Mk 1 NT5E face plate (my old master socket which OR chap left me) to get the phone to ring without a 'dangly filter' .

A normal DSL micro filter, dangly or otherwise, serves several purposes...

1) it prevents the attached apparatus from passing interference back into the DSL.

2) It prevents the DSL signal from causing audible artefacts on phone.

3) It generates a 'ring' signal for attached telephones.

A traditional  'master socket', ie NTE 5, will function as per (3) in generating the ring signal, and will make old fashioned phones ring.   But it won't provide any filtering per (1) or (2) hence won't stop the attached telephones from impacting DSL.   It may also allow bleeps and whistles to be audible.

If the affected segment of phone wiring is already filtered from DSL of course, that would be a different matter.   Apols, as always, if I have misunderstood.   

[Dray]

It is the presence of the 1.8 microfarad capacitor (part of the RC shunt across the pair) that is providing a locally generated signal to ring the bells and not the Mk 1 SSFP. I would remove the latter and just use the basic old NTE5/A as an extension socket.

Wouldn't a dangly microfilter also have an RC shunt across the pair, to generate the ring signal?

[roseway]

Perhaps Roseway or WWWombat could provide the relevant equation, please?

Not me, I'm afraid. I could have told you 50 years ago.

[Dray]

Don't you just add them up?
https://www.kitronik.co.uk/blog/how-to-calculate-capacitors-in-series-and-parallel/

[4candles]

With the new NT5E Mk3 face plate there is not bell wire so as I have said before I had to use a (untidy looking) plug-in dangly filters to get the bell to ring on my old land line phones.

You could use a filtered extension socket, like this standard one, or this larger one.

[burakkucat]

Wouldn't a dangly microfilter also have an RC shunt across the pair, to generate the ring signal?

Based on those that I have internally examined, I answer "no". They have only had a capacitor between the B-wire and the (so-called) bell wire.

[Dray]

Some of the microfilter circuit diagrams I've seen show a capacitor across 2 and 5
http://www.wirelesswaffle.com/images/microfilter_circuit_diagram.gif

[burakkucat]

That example is not of a typical microfilter and the capacitor you have mentioned is not for the transference of an AC current to the so called "bell wire".

[Dray]

I have no idea what that capacitor is for, but lots of microfilter circuit diagrams include it none the less 

[tickmike]

Just to make clear my BT (underground) drop-wire feed goes to one of the new O.R. Mk3 filtered NT5E outlets with the DSL socket at the top and below a phone socket and the usual 'test' socket behind the lower face-plate.

All my many phone sockets (including the new one in the workshop With the old NT5 master socket complete with it's circuit board ) are feed from the above MK3 master.

As another experiment I got together 10 'Dangly' plug-in filters and plugged them in 10 phone sockets,
I first looked at DSLstats then checked with all the filters plugged in, also including my workshop phone, two other landline phones and dect phones.
There was NO difference in my broadband stats and all connected phones rang and worked as they should.

The Capacitor in the Dangly filter is for the ringing current.

see   http://www.wppltd.demon.co.uk/WPP/Wiring/UK_telephone/uk_telephone.html

[sevenlayermuddle]

If the whole segment of circuit is already filtered from DSL then I don't foresee a problem using old master sockets, instead of danglies, to generate the ring signal.

It is true that the combined effect of the resistor and capacitor will load the circuit and may in theory reduce voice levels.  But being filtered, it shouldn't affect DSL.

There was a time about 40 years ago (vs Eric's 50 years ) when I could quickly have reeled off the impedance of a series RC for a given frequency.    But even without that, the overall impedance of a series RC cannot be less than the R.  Assuming the R to be 470k as has been stated, I feel certain its effect will be immeasurably small.

[burakkucat]

I have been thinking about using the old NTE5/A as an extension socket.

I would be tempted to dismantle it and remove the 470 k Ohm resistor from the circuit. Just leave the 1.8 microfarad capacitor between the B-wire and the "ring wire".

Also don't bother fitting the old SSFP to the old NTE5/A. It serves no purpose other than to increase the amount of protrusion measured from the backing-box!

[tickmike]

I have been thinking about using the old NTE5/A as an extension socket.

I would be tempted to dismantle it and remove the 470 k Ohm resistor from the circuit. Just leave the 1.8 microfarad capacitor between the B-wire and the "ring wire".

Good idea, not sure if it's a sealed module, I will look.

Also don't bother fitting the old SSFP to the old NTE5/A. It serves no purpose other than to increase the amount of protrusion measured from the backing-box!

I did not.