Hi Soms, yes I am a CSE, been on the broadband side (on top of "proper" faults )for 3 1/2 years now
If there's an issue with the internal wiring from the NTE about half the time it's due to the bell wire on it's own. When you look at the basic circuit diagram for a radio, it has a good resemblance in part to an nte, particuarly with the bell wire.
The choked plate tries to get around this problem, as I mentioned before you can reconise one either by the flap at the front being a slightly off white-grey tint. unless it already came with an nte with the openreach logo. other wise look for a small (I think I mistyped it as smell before, soz) cylinder behind the plate.
If the problem is caused by the other pair of wires (terminated in ports 2 & 5) then you would look at the dsl/ssfp front plate. The one with both a telephone & dsl socket on the front much like a micro filter.
The micro filters let the dsl signal go straight through them, the filters are there in case any equipment such as phones faxes, sky boxes,etc act like a radio reciver (by radio I mean any electrical noise, not bbc broadcasts & the like) & throw some of this noise on the phone line. If it's some thing the broadband can hear then it affects the quality of your connection to the net.
Also some times your equipment might hear the dsl signal & convert it to something you can hear so the microfilter prevents you trying to have a normal phone conversation over some horrible squealing & shushing noises.
This can come through either the bell or voice (other 2) wires.
As Roseway has said, some phones will respond to the ringing down the line without a bell wire. if you have the bell wire disconnected for any reason then microfilters have a capacitor within them which will still allow any bit of equipment to ring on an incomming call regardless if the equipment needs a bell wire or not.
Using CAT3,5,or 6 cable means you're less likely to pick up interference via the cable, it's really intended for digital data signals, the extra twists on each pair of wires mean one cable is less likely to overhear a nearby similar digital signal. Hence the're common in commercial networks where there are lots of data cables in close proximity.
As to wether old internal wiring or pristine new wiring would give you a better result for broadband, It's mainly luck. If the wiring is in tune/harmony with some noise source. You'll have an issue.
Don't know if this makes things clearer, ho hum..........
