Determine 4p4c wiring
UPDATE:

On rereading it's not obvious where you are connecting this or what it is you are connecting.

If this is a headset cord (as it seems to be) then what I said about voltages is wrong. 

What are you connecting to what?



OLDER:

Nothing makes sense.

If this is to a "central Office" you should have 50V DC somewhere.
 If to a PBX possibly 25 VDC or lower.

1,3 = 4.2V and 3,1 = 395 mV suggests that you are grounding the signal with your scope ground in the second case. You need a differential probe or isolated scope or measurements relative to ground.

Connecting ground to one wire will unbalance a feed circuit and allow induced noise from all over. Balanced load or feed must be used. 

Use a magnetic earpiece of around 1000 Ohms or a high impedance one with a say 470 Ohm resistor across it. Connect to 2 wires at a time and listen for dial tone. Go from there.