1. Cable of each pair + Voltage of powered detector
2. Your doing this when the mains is removed ?
3. Your SDP will then be "final exit"
4. BSIA
5. Make something ?
I nearly bought a scope some yrs back to fault find a CCTV job, they used to be very expensive CRT things.... But now a few a thundred quid.
I'd love one but have no practical use for it.