[NA]Lightning and Modems[NA]

[Let'sgoflying!]

Every time we get a dark cloud move by, our standard dance is to run around the place unplugging electronics.....apparently we are high on Mother N's list for "Who to Send a Bolt Out of the Blue To", and get a lot of hits each season. The occasional time I am absent, or just too slow, we lose the DSL modem.

The first time, it was warranteed. The second time, I unplugged only the power supply never thinking it could be coming from somewhere else. The last time, they recommended a surge protector (for their failed unit, which was damaged by electricity they admit came in on their phone line).

So I have one in now but got to wondering why only the modem gets hit, and not any of the 6 phones in the house; arent they all electronic too? Or the 3 or 4 caller ID units I have plugged into the phone line.. heck I think even the TV is plugged in!?
And why don't they install a surge protector in all the modems at the factory??

 

[RJM62]

The simple answer to why DSL modems are more likely to suffer lightning damage than phones is that a DSL modem is far more sensitive and uses much, much lower voltages and currents. A conventional (not VOIP) telephone's audio signal, on the other hand, still uses the same old analog technology that your grandmother's old phone used. (A direct hit close enough to your home probably would take out the phones, though.)

The reason that modem manufacturers don't build lightning suppression into modems is because it's not technically feasible to do so and could actually make life more dangerous. Lightning protection, like surge suppression, requires a good path to ground; and there's no way a modem manufacturer can insure that the user wouldn't use an adapter to bypass the ground feature, run the modem on a cheap lamp-cord type extension, etc.

But although they both require grounding, lightning protection isn't the same as surge suppression. Contrary to popular belief, ordinary surge suppressors are not rated for lightning protection. That's not to say that they won't help at all, especially if the lightning doesn't directly hit the wire or hits it far enough away. But they're not rated to protect you from a direct hit on your feed.

Lightning protection is best accomplished before the wire enters your home. The hardware to do this is not expensive, nor is the work particularly complex. It basically consists of placing the lightning protection device between the wire and your house, and grounding it to a good earth ground.

The protective devices themselves are commonly called "lightning arrestors" or "lightning suppressors." They are not the same thing and there are several different types (semiconductor, gas tube, or hybrids of the two being the most common, although there are others), but either type of device, if installed properly, should afford adequate protection for wired telecommunications connections. (Radio masts are a whole 'nuther story, but we're not talking about that.)

There are several companies who specialize in lightning protection. One of the more dependable ones I know of can be found here, but most industrial electrical supply houses also carry these products.

Rich