Communications Circuit Protectors

The protector is a small sacrificial device at the point of entrance that clamps or shorts a dangerous surge to ground before it travels inside. It is required based on how exposed the cabling is to power and lightning.

With fiber and buried service this matters less than it did in the copper-everywhere days, but any exposed metallic pair still needs that protector standing guard at the door.

When it applies

Where communications wiring runs outdoors or could contact power conductors or take a lightning surge, a listed primary protector goes in at the building entrance. It clamps and diverts dangerous voltage before it rides the pair into the premises wiring.

Common mistakes

• Skipping the protector on an aerial or exposed run because the phone still works fine on a clear day.
• Leaving the protector's ground undersized or too long, so the surge cannot get to earth fast enough.
• Bonding the protector ground to a different electrode than the power system, creating a difference of potential during a strike.

In the field

On a rural comms drop I bonded the entrance protector's ground straight to the building's grounding electrode system with a short, direct conductor. That single bond is what keeps a nearby lightning hit from pushing thousands of volts down the line into someone's equipment. Common bonding at the entrance is the whole game with these protectors.