Second off - I need to be upfront and say this is about my day job - and not diy phone wiring.
Basically, I'm going to be testing some prototype high speed (200Mbps) modems, and as well as test rigs that match up to standard modern practice - I also want to build a rig that reflects poor but all-too- common wiring too.
I'm particularly thinking about Victorian blocks of flats (like London tenements) that were never built with wiring in mind. So the phone wiring to the flats might be drop wires bunched together, with more and more of them added ad-hoc as more phones were connected.
Even more so if the ad-hoc wiring happens to be crammed together with mains wiring (although wiring regs says in shouldn't be!)
If you can spare a couple of minutes to tell me about it (particularly if you know the wiring layout around the building) - I'm really interested!
The only other way I can find out is to peer around blocks of flats, tracing wiring, making sketches and getting arrested. I'd be very grateful if you told me about it instead!
Explanation for those that want to know what's going on:
FYI - these are high speed modems that use the existing copper wire from your house/flat to the pole (or whatever - the place known as the CN - convergence node), where there's another box - followed by bonding of lines back to exchange/central office).
Hence the wiring length in original copper is usually less than 100m, hence it can support much greater speeds - provided that it doesn't pick up masses of electrical noise.
For those not familiar with how this stuff works - phone drop wires consist of a number of twisted pairs - i.e. two insulated wires twisted around each other into a spiral, before being laid next to the others and the outer cable jacket applied. This improves the noise immunity of the wiring because each of the wires in the pair should be affected equally. Twisted pair wiring is then used with differential signalling i.e. the signal is the voltage difference between the two wires in the twisted pair. This works to a degree - if the source of interference is too close or too big, the signal can still be excessively affected.