Phones systems & passive tapping of twister pair

[Whales]

I have a network closet with mostly a tangled mess of ethernet and some occasional phone lines woven in (some PBX, some POTS).  I want to untangle it all and properly separate & clearly label the POTS lines, especially since it looks like one might currently be plugged into a gigabit switch.   

Yeah.  I'm looking forward to finding out for sure.  Let's hope it's not.

At the moment my plan is to spend a few hours with an old landline phone IDing the pots lines and labelling them with their phone numbers.  Whilst I can deal with the ethernet mess, I'm not a phone tech.

Q1. Any interesting phone-related resources that are suggested reading?  I'm familiar with what a ringing voltage is and how I don't have perms to do anything past that plug; but I've never read any formal sources of info. 

For example: Are there relevant publicly-available walls of advice or standards for POTs in network cupboards?  Eg minimum protection reqs, cable routing reqs, etc.  At the moment my searches are returning pictures of crockery in drawers.

Q2. Are passive twisted pair taps for phone/audio freqs a product that exists?  EDIT: to be clear, not a wired splitter.  I'm imagining 0-8KHz audio (intrinsically AC coupled) taps, using a short coil pickup you place near the cable or a capacitive pickup/probe on the cable jacket.  Twisted pair isn't infallible, esp at close range, but I can't find even a tiny bit of literature about the idea using my current search terms.

This last one is out of curiosity.  Using an actual plug-in phone is good enough for what I want to do, but I thought I can't be the first person to think of "truly" passive phone tapping.

[soldar]

Pots identification is simple and straightforward. Just connect a phone set with alligator clips or any other way. Even if you do not have a phone set you can just measure voltage because it will be about 48 Vdc when the phone is on hook and fall to a few volts when the phone is off hook.

[Whales]

Thanks for the tip. 

I presume most old-fashioned PBX systems also provide phantom power, so the handsets don't need any other wires/plugpacks to work, so I'll still have to do other checks to ensure I'm not chasing the wrong system.