The MLP-050T protects the equipment when the voltage on the pair rises above 56V. It also opens the line when the current goes over 150ma. When the voltage or current goes back below the threshold, the MLP-050T automatically resets.
You should order a Ground Lug to attach the ground wire to the screw on the side, or you can order a Wall Mount Ground Bus & Lug to mount the MLP-050T to the wall with up to 6 Protectors (for 6 Lines).
If you don't know the voltage on the line (and there is no ring voltage), put a DC volt meter across the pair to determine the voltage that's on the line normally, then choose a protector that has a higher voltage threshold than what you read (by at least a couple of volts).
Our MLP Protectors come in the following thresholds: 14V, 21V, 30V, 56V, 70V, 110V, 123V and 270V.
You'll need one Protector for each pair.
If you're putting this on a line going to another building (OPX), be sure to put them at BOTH ENDS of the cable leaving the buildings!