problem between power and communication cable

Other responders have assumed a myth: "surge protector = surge protection". They have assumed a protector will stop, block, or absorb transients. For generations, such solutions have never been effective. Generations ago, we routinely suffer no damage because we don't even try to stop, block, or absorb transients. We use what Ben Franklin demonstrated in

1752.

Protection is not the protector. Protection is earth ground. A protector is effective IF it connects a transient 'less than 10 feet' to the protection - earth ground. Those other recommendations don't even discuss earthing. Rather embarrassing.

A figure from the NIST (National Institute of Standards and Technology) may demonstrate your problem. The fax machine is damaged because protection is not properly located and installed:

Protection is not those protectors - power strip or UPS. In the NIST figure, the protection on each incoming utility wire is not the same single point earth ground. That single point is one essential requirement of effective protection. Every incoming utility wire (including communication and power - whether buried or overhead) must enter a building earthed to a single point. An earthing connection must be via surge protector (AC electric and phone) or using a hardwire (CATV which requires no surge protector to make that connection).

Phone lines typically have a 'whole house' protector installed for free by the telco. Why? 'Whole house' protectors are so inexpensive and so effective. But that 'whole house' protector - again - will only be as effective as the earth ground provided by your building. That NIST figure demonstrates why.

If all incoming utilities are earthed (via protector or hard wire) to the single point earthing point, then no voltage gradient exists inside your line card to cause damage. If all inputs are raised to 10,000 volts simultaneously, then there is no voltage transient to damage transistors.

Again, we don't stop, block, or absorb surges - such as that UPS recommendation implies. How would that UPS stop what miles of sky could not? It's manufacturer does not even claim that ability. He simply hopes others will promote a myth - that the plug-in UPS provides protection from the other typically destructive transient. Create equipotential so that the line card is not damaged. Plug-in protectors cannot do that.

The most common source of modem damage is AC electric. In fact a most common damaged part is the PNP transistor that drives the off hook relay. Why? The PNP transistor conducts the transient when both AC electric and phone line are not earthed to the same single point earth ground. Others who did not learn how damage occurs will still recommend useless plug-in protectors.

Again, phone lines already have an effective 'whole house' protector. But AC electric is the one utility that connects wires highest on the utility pole (most often struck) directly into modem. Furthermore, an adjacent protector can even make this damage easier.

CATV and phone lines already (should) have effective earthing connections as even required by National Electrical Code (you should verify this). But AC electric is not required to provide transistor protection. The homeowner must install a 'whole house' protector on AC mains (at a cost of less than $1 per protected appliance). Numerous 'whole house' protectors are available from Leviton, Siemens, Square D, Furse, etc. One is sold in Home Depot is Intermatic IG1240RC.

No effective protectors are sold in Lowes, Sears, Kmart, Walmart, Staples, Office Max, etc. How do you know? Two simple rules: 1) the protector does not have a dedicated connection to earth ground AND 2) the manufacturer (ie that recommended UPS) does not even discuss essential earthing.

The bottom line: A surge protector is only as effective as its earth ground. No earth ground means no effective protection. Modem damage is so easily avoided as to be considered directly traceable to human failure - such as those who recommend plug-in protectors.

11 wrote:

Buy a good grade of UPS with good power protection in it. Run the phone line through the provided phoneline jacks on it. Burning out of modems is usually from nearby lightning strikes. Replace the surge suppresser annually,

as the protection devices get used up.

--Dale

Dale Farmer wrote in news:420B9C51.97255903 @cybercom.net:

Or just buy a non MOV based surge protector (more expensive, but they won't wear out).

Hah-hah-hah! Used up! That's like the guy at MIT who borrowed the screwdriver, and shorted out a bus bar in the computer with it, taking a bite-sized chunk out of its blade when it arced. When he brought it back, he said it was "used up"! :-P

Or better yet, don't waste your money on ineffective surge protectors that are built into the power strips. They depend on an excellent ground, which most dwellings don't have. Put the surge protector on the main breaker panel where it belongs. That's where the lightning surges come from.

[snip]

I'll agree with that 100 percent!

[snip]

I've just removed some of his verbiage that tends to turn people off after reading the first sentence.

Bottom line is that the $3 power strip with 50 cents of worthless parts in it, sold as a $30 to $50 surge protector, is _pure_profit_ for those radio scrap and best buy stores out there that sell you one of those with your computer system.