Connect with us

*TOTALLY* isolating phone from line, electrically?

Discussion in 'Electronic Basics' started by Don Bruder, Dec 10, 2003.

Scroll to continue with content
  1. Don Bruder

    Don Bruder Guest

    OK folks, here's a little something that just blew through this disaster
    area I call my mind. Tossing it out for the idea of determining

    Lightning kills computers and computer gear. We all know this to be a
    pretty well established fact. We also know that, in most (not all, but a
    very large percentage) cases, the lightning damage didn't come from the
    power lines, which are, in general, pretty well protected, either by
    compliance with well-researched/written building codes, requirements for
    grounding a specific way, surge suppressors (both on the pole and within
    the house) and so on. Indeed, most lightning damage seems to come into
    the building by way of the phone line, which is nowhere near as heavily
    "regulated and sheilded" by building practices. Phone wire runs the
    lightning right into the house, cooking off whatever is attached
    directly, and sometimes nearby items. Usual scenario: phone line takes a
    hit, modem fries, takes computer's serial ports (or even more of the
    motherboard) with it.

    With that in mind, I've just had something resembling a brainstorm, and
    want to bounce it off this merry band of electrical lunatics to see if
    it's at all practical.

    Since the phone line is (or at least, for the sake of this discussion,
    I'm "ASS-U-ME"-ing that it is...) the most frequent route for a
    lightning hit to follow and cause damage, it seems to me that
    electrically isolating the phone line from the house and contents would
    be the best route to take. As of right now, I'm *REALLY* hazy on the
    details, but the seemingly ideal implementation would be a box (black or
    otherwise...) which plugs into the demarcation point (the place where
    the wire from the pole connects to your house, if you're not up on
    phoneco lingo) then everything else in the house that needs/uses a phone
    line plugs into that.

    Anybody ever heard of/encountered such a beast?

    If one exists, what would you expect/be willing to pay for it, and who
    would you look to in order to source it?

    If no such thing exists, has anyone got a good explanation for why not?
  2. I've never heard of one, and I can think of several reasons why not right
    off the bat.

    Telephones use several different types of signals for different purposes.
    They use high voltage, low frequency pulses for ringing, there's an offhook
    voltage, and there's an onhook voltage. A device that you would create in
    order to do this isolation would need to somehow process those signals,
    isolate them (perhaps, no, probably, using optoisolators), then regenerate
    them on the house side.

    The regeneration would require power.

    The power would come from... say it with me... line current.

    Which lightning could cause surges in.

    No more isolation.

    Also, lightning could easily fry the circuit before the isolation, and arc
    across the optoisolator pins, frying the internal circuit. So, now,
    instead of having one point of entry (assuming the phones aren't powered,
    which is a really poor assumption these days), you have two.

    The only real way to isolate telephones from the external network is to pull
    the plug, or perhaps include a heavy duty switch that gets tripped when
    lightning is detected (heavy duty enough that even if it gets a near direct
    hit by lightning it won't arc, though the EMP might fry things anyway...)

  3. Don Bruder

    Don Bruder Guest

    Understood, accepted, and at least *PART* of why I'm wanting commentary.
    That's a given...
    Ahhh, but line current from what source? NOTHING says that the phone
    line has to be the power source for this box, and in point of fact, I'm
    thinking that the device would be *MUCH* more robust if it were run from
    mains (with appropriate transformation, rectification, filtering, etc)
    or other "non phoneline" power source.
    Perhaps, perhaps not... recall that I'm operating from the premise that,
    in most cases, the phone line is going to be the one affected by a
    strike, with the power lines almost always being well-enough protected
    that anything less than a direct-to-the-wire hit on the wires between
    the transformer and your house is *PROBABLY* going to be a non-issue.
    Only true in cases where the phone line itself is the power source. See
    Errr... Huh? You lost me. I understand the possibility that the hit
    could jump the optoisolator, but the rest of it just left me wondering
    what it was that you actually said.
    I flatly refuse to accept that. "Nobody's done it, so it can't be done"
    didn't hold any water when Columbus set sail from Spain, it didn't hold
    any water when Kennedy said "let's put a man on the moon", and it
    doesn't hold any water today. Only a very few things are impossible, and
    even those are questionable.
    EMP is, of course, a concern, but at least for my purposes, there's very
    little, if anything, I can do about it. If a hit is close enough to
    generate sufficient EMP to knock something out, chances are scary-high
    that the device that fried is going to be the least of your worries,
    since the house is probably burning down around you as you stand there
    pondering your fried phone equpiment.
  4. Jerry G.

    Jerry G. Guest

    That was an excellent explanation!

    I was going to suggest the simplest. He should get a cell phone, and let
    the problems be with the provider. There are some new technology cell
    phones that can be used as a semi-highspeed modem with a computer. These
    are very effective for wireless email and general browsing.

    It will be his luck that the cell phone would be on the charger, the next
    time lightning hits his power line! I can just see it now...


    A few years ago, I was watching TV in the living room, and my wife was
    watching another program in the bed room. There was a loud crash on the
    side of the house, that almost put me on my butt! I ran to the bedroom, and
    my wife was shaking in fear, and the air conditioner was smoking like it was
    on fire! Lightning hit the dammed air conditioner! It was burned up
    inside! The outside of the building had all black colour in the bricks near
    the air conditioner. The air conditioner was scrapped.

    What gets me, is that the air conditioner has a heavy metal box enclosure,
    and was grounded through the AC line. How did it get burned up inside???
    All the motors were fried, including the compressor. I had the machine
    checked anyways to know what failed when it got hit. As a safety
    precaution, I changed the AC outlet that it was plugged in to. But, the
    conclusion was that lightning hit the air conditioner somehow. There was a
    big burn mark on one corner, and some of the metal on the edge of the case
    was melted!

    After some arguments, I managed to get the insurance company to pay for it.
    I found out the hard way that the claim was not worth the effort. I paid
    about 3 times for it, just in the increase!



    Jerry Greenberg GLG Technologies GLG

    I've never heard of one, and I can think of several reasons why not right
    off the bat.

    Telephones use several different types of signals for different purposes.
    They use high voltage, low frequency pulses for ringing, there's an offhook
    voltage, and there's an onhook voltage. A device that you would create in
    order to do this isolation would need to somehow process those signals,
    isolate them (perhaps, no, probably, using optoisolators), then regenerate
    them on the house side.

    The regeneration would require power.

    The power would come from... say it with me... line current.

    Which lightning could cause surges in.

    No more isolation.

    Also, lightning could easily fry the circuit before the isolation, and arc
    across the optoisolator pins, frying the internal circuit. So, now,
    instead of having one point of entry (assuming the phones aren't powered,
    which is a really poor assumption these days), you have two.

    The only real way to isolate telephones from the external network is to pull
    the plug, or perhaps include a heavy duty switch that gets tripped when
    lightning is detected (heavy duty enough that even if it gets a near direct
    hit by lightning it won't arc, though the EMP might fry things anyway...)

  5. Line current == mains current in US. What we have here is a failure to
    Fair assumption, but only an assumption.
    True if the prior assumption is correct.
    I was referring to the fact that if the device is mains powered, you have
    two failure modes rather than one - two points of entry into the system.
    Good luck. I don't know of any, and these are good reasons it'll be
    Depends where it hits. Lightning is a tricky bugger and rarely does what
    you expect.

  6. I used to live in Toledo, Ohio. One of the strange things about that area
    was that occasionally a thunderstorm would come through that was unusually
    electrically active. And that, by the way, is an understatement. I mean,
    the kind of storm where CG lightning hits all around you (and CLOSE, too)
    about once every couple of seconds and the cat and dog would go hiding
    under the couch.

    I understand a great deal about the mechanics of thunderstorms but I really
    would like to know what makes a thunderstorm do that.

    Anyway, I remember two such storms. The first storm, I was about 9 or 10
    years old. My parents were having some marital issues, and we, for some
    reason, left the cat with a family friend while they were hashing them out.
    Well, we went and got the cat, and on the way back, one of those
    thunderstorms hit. We put the car in the garage, which was right next to
    (about four feet from) a telephone pole. I ran to the back door with the
    cat, opened the door, went inside, and about ten seconds later lightning
    hit the telephone pole outside and made the telephone ring. That was

    Oddly enough, the telephone survived, and there was no damage to anything,
    but I'd say at least 100 volts went through the telephone line.

  7. Don Bruder

    Don Bruder Guest

    OK, gotcha. We were heading for the same store, just took a different
    road to get there. I was reading your "line current" to mean the
    phoneline current, since the context of the discussion was phones and
    phone lines.
    True, it is an assumption. But where else does one start? :)

    For the most part, it seems to be a safe assumption, though. The amount
    of lightning absorption/dissipation/other protection on power lines is
    positively unreal when you actually start paying attention to what's
    there. And it has to be - Power lines are such a huge potential target
    for a lightning hit that if they weren't heavily protected, a storm
    would take out the juice for miles upon miles of countryside with just a
    single hit. I've yet to see a strom that was satisfied with only
    dropping a single strike, which in turn means that mega-heavy-duty
    lightning protection *MUST* be in place, otherwise, whole sections of
    the country would be dark almost constantly. Florida, with its daily
    thunderstorms at about 4-5 PM leaps to mind as a prime example - 4-ish
    rolls around, thunderclouds start moving in. By 4:30, 5 at the outside,
    it's pouring rain, flashing like a disco, and otherwise looking like the
    end of the world. By 5:30 or so, the rain is done, the clouds are
    almost, if not completely, gone, and the sun is turning the place into
    the world's biggest sauna - yet the only time during the year I lived
    there that we lost power (not counting 2-3 second flickers) was when one
    storm hit several trees on the property, one of which fell on the wires
    and snapped off a total of 8 poles, leaving us without power for close
    to a week as the power company tried to get gear in that could reset
    them. (swampy area - pole-setter trucks kept hitting soft spots and
    sinking past the axles before getting to the locations they needed to be
    in to get the job done - After 4 tries in as many days, and still not
    even halfway done, they finally gave up and dragged some kind of
    tank-like military gizmo out of mothballs, and it went in on crawler
    tracks to get the job done)

    Ahhh... comprende. But that goes back to the initial assumption: That
    the power lines are *PROBABLY* protected better by the electric company
    than any precautions you or I can practically apply once the wire hits
    the house. I'm thinking that the risk of failure on the power side of
    things is vanishingly small when compared to the danger that anything
    connected to the telephone line is exposed to.
    Heh... You're showing your "glass half empty" streak :)

    I'll take it as a challenge and see what I can come up with. Let ya know
    as things progress.
    That's a definite fact! I'm assuming (Oh gawd, not another
    assumption...) that for a strike to generate sufficient EMP to be a
    danger to the health of electronic devices, the strike is going to have
    to be pretty darn close - as in practically right on top of whatever it
    is that gets fried. Otherwise, the inverse square law, and possibly
    others, applies to pretty much rule out any damage from more distant

    <grumble> 7 modems, a serial port, and a computer in 3 years... There's
    GOTTA be a way of protecting them that doesn't involve me babysitting
    them 24/7, or idiocy like having to unplug them after every use.
  8. Don Bruder

    Don Bruder Guest

    Great concept, 'cept for one minor detail:
    I'm way rural, and on top of that, located in a sort of natural "bowl"
    formation that kills cell phone (and TV, and radio) signals. The only
    way any kind of signal gets to the house is over a wire, or off a
    satellite dish. Over-the-air broadcast signals just don't make it in.
    Even if it weren't for the "bowl", cell coverage starts getting
    seriously "iffy" about 7-8 miles from the house - that's not really a
    topographical/transmission problem, just a lack of any cell towers
    closer to us than about 15 miles.

    And no, I ain't interested in moving to the shitty^H^H^H^H^H^Hcity so I
    can get cell-reception! I happen to LIKE living out here in the
    boondocks, far, far away from the idiots and general insanity that city
    life forces one to endure.
  9. More like my "latent engineer" streak. Prepare for every eventuality.
    That's one reason why I'm still alive, at least so far :) Especially
    considering how many televisions I've had my fingers in while powered up as
    a preteen.
    Good luck. Don't get too discouraged if it doesn't work.
    Do you have telephone surge protectors connected to them? Those will at
    least provide a small measure of protection.

    I have a UPS with telephone surge protection. Living in the northern part
    of tornado alley, where electrically active storms seem pretty darn common
    (but so far less active than the really bad ones I wrote about in another
    thread), I'm darned glad I have it.

  10. Don Bruder

    Don Bruder Guest

    You too, eh? Only mine went well past "pre-teen"... Sometimes you just
    *HAVE TO* have the juice on in there to make a diagnosis. Kinda hairy
    sometimes, but when it's the only way to do the job...

    (Got bit by the suction-cup thingy - What *IS* the proper name for that
    thing, anyway???? I've heard it called everything from "anode cap" to
    "aquadag", but almost never the same thing twice - exactly ONCE. After
    that I learned that the old "one hand in TV set, one hand in hip pocket"
    advice was much less inconvenient than writhing on the floor in pain for
    several minutes, and not being able to pick up anything with the "bit"
    hand for half a day.)
    Don't be so encouraging!!!!

    On the plus side, a google search netted me a phone line isolator
    patent, dated 1998, that SOUNDS good. If the beaureaucrat-ese in the
    claims has any resemblance to real-world behavior, it should be the
    *TOTAL* electrical isolation I'm hoping to find. Now if I can just
    figure out who (if anybody) has licensed it and started making/selling
    the beasts...

    Failing that, I may just break down and buy a copy of the patent (which
    claims, although I haven't been able to get 'em to load, to have
    schematics and all the info needed for a working prototype) and build
    one myself. Don't bother me with "that's illegal". Frankly, I don't
    care. Somebody wants to come after me for patent infringement over
    building one widget, they're more than welcome - They might even win,
    and congratulations to 'em if they do. But the simple fact is you can't
    squeeze blood out of a rock.

    (Close-enough-to-bankruptcy is pretty much a bulletproof defense against
    idiots with more lawyers than brains - If I've got nothing to begin
    with, whatcha plan on taking away from me?)

    The first dead modem bought it while connected via one of those. The
    second modem exploded (literally - blew chips into fragments, cracked
    the case, and blasted popcorn-like capacitor contents all over the
    place) while connected through TWO phone-line suppressors. At that
    point, I gave up on them as a waste of time, money, and effort.

    Fuse - n: The 15 cent part that the only 500 dollar part in your project
    will protect from overvoltage/amperage conditions by exploding.

    Surge Suppressor - n: The 15 dollar part that will be protected from
    voltage spikes, lightning hits, and similar calamaties, by the
    multi-hundred dollar dollar computer system attached to it exploding.
  11. Dbowey

    Dbowey Guest

    Some of the posted insight included:
    those are questionable.
    You won't win an argument with fluffy rhetoric. What you are in need of is a
    "Protective Connecting Arrangement." It's been done before...... search on
    that and just "PCA." PCAs were required by the neurotic Telcos to protect
    their facilities from the naughty, bad customer owned equipment. The
    "protection" worked both ways. I believe it was in 1984 the FCC began the
    Registration Program and mandated the Telcos to quit using PCAs. My first
    point is that what you wish to do is not entirely new, but is, in my opinion, a
    poor idea.

    My next point is that, unless you get the industry to create a new Network
    Interface spec (meaning all of the technical parameters of the Network signals
    and the Customer Installation signals at the interface, then you MUST use the
    interface definitions that now exist. You can find all of them in FCC CFR 47,
    Part 68 and also find useful insight in the ANSI Standards for the types of
    services in which you have an interest, such as Loop-Start and Ground-Start

    When you finish with your research on this, doing the latter will cause you to
    create a piece of equipment containing all the protective elements than now
    exist in residential terminal equipment, so then, lightning can blow hell out
    of it instead of blowing the phones and modems. It would need to be customer
    owned equipment....... the FCC will not permit the Telco to own it, so it would
    neccesarily need to be Registered.

    As to working with the industry to define a new, protected interface, do a
    search on Committee T1. Committee T1 has Technical Subcommittees (TSC),
    attended by manufacturers, Telcos, Special Interest Groups, Interexchange
    Carriers, etc. The TSCs have Working Groups who are charged with doing the
    technical work. TSC T1E1 writes Network Interface Standards.

    Read about them, see who are the contacts, and work with them. They may or may
    not agree with you. In any case, these are the people who will eventually
    decide if it's worthwhile.

    And finally, they like facts. Fluffy dialog won't go far.

  12. Dbowey

    Dbowey Guest

    Don Bruder posted:
    Have you sorted out whether the surge is from the Power line or the Telephone

  13. Harry Muscle

    Harry Muscle Guest


    I didn't read the whole thread, but have you looked into whole house surge
    protectors. They can be professionally installed into your breaker box and
    protect both the power lines and phone lines (and sometimes even the cable

  14. w_tom

    w_tom Guest

    One example of how CG lightning is created AND, for example,
    why 'tornado alley' does not typically suffer so often from
    this destructive type of lightning.

    Take a cumulus cloud. Let high speed upper atmosphere winds
    blow the top of that cloud well ahead. Anything that falls to
    earth (rain, hail, etc) would contain electrical charges from
    the top of that cloud. Now we have a cloud bottom that is
    three miles up and four miles behind the earth charged
    region. CG lightning will make a connection from bottom of
    cloud to those earth borne charges.

    However it will not take the 5 miles path. 5 miles through
    non-conductive air is electrically longer than 3 miles down
    and 4 miles through earth. And so we have power lines that
    make that connection, through power line, into house, through
    appliances (especially modems, portable phone base stations,
    and faxes), to earth via phone line (because unlike AC
    electric lines, the phone lines routinely have 'whole house'
    protectors installed). Therein lies an example of how surges
    damage electronics.

    Much must be cited to contradict so many urban myths.
    First, lightning is electricity. Therefore from primary
    school science, first a complete electrical circuit must
    exist. Before anything is damaged by that surge, first the
    surge must pass through everything in that circuit. Too many
    myth purveyors will say lightning entered on phone line,
    damaged modem, then stopped - in direct contradiction to
    science taught in primary school.

    Second, that complete circuit means that something must have
    both an incoming and outgoing electrical path; else no surge
    damage. Why surges do not damage DRAM, for example. A surge
    that passes through motherboard, and then modem, to obtain
    earth via the phone line does not damage all those other
    motherboard semiconductors. Those other semiconductors had an
    incoming path but not outgoing path.

    Third, lightning has traveled how many miles through
    non-conductive air. Is a silly little isolation transformer
    going to stop (or absorb) what miles of non-conductive air
    could not? Of course not. Any surge protector that claims to
    stop, block, absorb, or filter a lightning circuit is simply
    scamming the naive. Surge protector as a 'dam' is not
    effective. Surge protector as a 'dike' can be effective. But
    that means the flood (surge) must have a better path
    downstream to earth ground. Surges can be diverted; not
    stopped, blocked, filtered, or absorbed.

    Summary of effective protection was demonstrated in 1752 by
    Franklin and proven in so many 1930s professional papers.
    Summary is discussed in "Opinions on Surge Protectors?" on 7
    Jul 2003 in the newsgroup alt.certification.a-plus or
    Detailed discussion including warranty, UPSes, low voltage,
    why computer fails, no protector required for cable, joules,
    "Power Surge" on 29 Sept 2003 in the newsgroup
    alt.comp.hardware or

    The most critical component of a surge protection system is
    earth ground. Many effective systems don't even require a
    surge protector. For example, that grounding block (properly
    located and earthed) on the CATV line provides the entire
    cable lightning protection - no surge protector required or

    Surge 'protectors' are not surge 'protection'. Those are
    separate components. A surge 'protector' is only another
    component that can make a connection to surge 'protection' -
    single point earth ground. Protection is a building wide
    system. This being the most important sentence in the entire
    A surge protector is only as effective as its earth ground.

    Importance (and it is an art) of effective earthing is
    discussed among engineers in two threads:
    Storm and Lightning damage in the country 28 Jul 2002
    Lightning Nightmares!! 10 Aug 2002 and

    And yes, if you thought surge protection was about some
    simple, retail, plug-in device ... well they count on you not
    knowing any of this - at great profit. Surge protection is
    earth ground. To sell those grossly overpriced, undersized,
    ineffective products - they avoid all mention of earthing.
    Try to find any mention of earthing on any plug-in protector.
    No grounding - earthing. No earth ground means no effective
    protection. Welcome to a science (and art) that was very well
    understood before WWII.

    Why was that spot in Toledo so CG lightning active? Start
    by learning the geology. Geology (and what we bury in it) is
    a major reason for where CG lightning occurs. Again and why -
    its all about earthing - not grounding - earthing.
  15. w_tom

    w_tom Guest

    I believe you are confusing the National Electrical Code
    with lightning protection. The NEC is written only for the
    purpose of human safety. It makes no effort to address
    transistor safety. The most common source of destructive
    surges - indeed the shortest and most direct path incoming to
    electronic appliances - is AC electric.

    We still build new homes as if the transistor did not exist
    - even 30 years after the transistor became ubiquitous.
    However, telephone connections inside the typical house is
    made via a 'whole house' surge protector - provided free by
    the telco. You can find yours in a box, often the NID,
    located (by code) within twelve inches of where the wire
    enters your building. And, of course, that surge protector is
    only as effective as its earth ground meaning that 12 AWG (or
    larger) wire must make a less than 10 foot connection to earth

    Again, the code is only concerned with human safety.
    Therefore the code says that ground wire must be less than 20
    feet. But for effective transistor safety, that wire must be
    less than 10.

    Posted elsewhere in this thread is much more information.
    Must of which will be in direct contradiction to so many urban
    myths - and yet was standard knowledge even before WWII. For
    example, your telco connects a $multi-million computer
    directly to overhead wires everywhere in town. Do they
    disconnect for thunderstorms? Or do they stop service for
    three days while they replace the $multi-million computer? Of
    course not. They too use simple 'whole house' protection
    methods. All incoming wires are first earthed before entering
    the building - either by direct connection or via a surge
    protector. Earthing - not surge protector - being the 'magic'
    solution. Earthing techniques so long and well understood
    that we should be building all new homes using Ufer grounds.
    Again, a technology probably long older than you - because
    effective surge protection was that well understood for that

    Benchmark in surge protection is Polyphaser. Their
    application notes are considered legendary. What do they
    discuss? Their products? Of course not. Polyphaser is
    selling effective protection. They discuss earthing ...
    extensively. A surge protector is also only as effective as
    its earth ground.

    Phone line appliances such as phones and modems already have
    the galvanic isolation you are seeking - typically rated at
    2000 or 5000 volts. So why does damage occur? That
    protection that also exists in computer power supplies and
    most every other household appliance assumes the building has
    a 'whole house' protection system. Something not required by
    any electrical codes. If the 'system' does not exist, then an
    incoming surge will overwhelm internal appliance protection -
    seeking earth ground, destructively, via that appliance.

    Even Home Depot sells effective 'whole house' protectors for
    residential AC electric - Intermatic EG240RC and IG1240RC or
    Siemens QSA2020. But and again, a surge protector is only as
    effective as its earth ground which is why those 'whole house'
    protectors are effective IF properly earthed - as discussed in
    those other threads listed in the other post. Effective
    'whole house' protection that costs about $1 per protected
  16. Ian Stirling

    Ian Stirling Guest

    Aquadag is the graphite-based paint that covers the majority of the back
    of the tube, except a small area around the anode cap, which covers the

    o1You can purchase optoisolated serial cardfs/
    You can also get optoisolators with two RS232 plugs.
    And even RS232 - optical fibre when you need hundreds of Kv isolation.

    You'd probably need to work out some means of powering the modem.
    A transformer cut in half with a bit of plastic/glass in the middle is
  17. Don Bruder

    Don Bruder Guest

    Since at least four of the dead modems showed obvious signs that the
    strike that wiped them came in through the phone line (traces from the
    phone jack vaporized, so-called "protective elements" directly connected
    to the phone jack traces, and so on, all cooked), I'm calling it a
    more-than-reasonable hunch. The other three... Well, to the best of my
    knowing, a wall-wart SHOULD cook off long before allowing a killer spike
    to get to through to whatever it happens to be powering. The warts are
    good (two of them in use as I type, one with different connector on the
    end powering my discman player, the other topping up a set of Ni-Cds),
    but the modems are toast. Best I can say is "make your own assumption".
    The cooked serial port card was obviously blasted from the direction of
    the modem (only device attached to it) and the computer was a "dunno
    how, but it's got burnt traces on the motherboard, so it's toast"

    Based on that info, if you can tell me which line the strike came from,
    you're doing better than me.
  18. Spajky

    Spajky Guest

    cheap & effective way is IMHO getting a surge protector for mains &
    phone line ( possibly for Lan connection too) in single box from which
    all my sensitive machinery gets power & other connections .

    IMHO it prevents (if house electricity grounding is Ok & properly
    done, should be!) almost 99% of surges.

    Will not protect against direct or very close lightning hit, but that
    are rare if you are not really a "hot spot" for it.

    mine saved my equipment few times in this few past years
    (I just replace blown fuses few times & than I replace the protection
    every few hits - every 2 or 3y).

    It works for me & is cheaper than my modem card.

    -- Regards, SPAJKY
    & visit site -
    Celly-III OC-ed,"Tualatin on BX-Slot1-MoBo!"
    E-mail AntiSpam: remove ##
  19. The only solution I can see would be to buy a bunch of low cost
    phones, and a good one for serious work. You can leave the good one
    unjacked when not needed. Leave a low cost phone in the wall jack in
    case you need to receive a call. If the phone gets blown out, you can
    toss it, and then use another spare. Most likely the phone will last
    a number of years before it gets blown by lightning anyways. You may
    even wear out the phone from use, before it gets hit by lightning

    Making all kinds of design changes to the telephone line, and
    experiementing would be more costly, and also most likely a great loss
    of time in relation to getting a number of good phones. These phones
    are all designed to be disposable anyways. If a new phone fails
    during the warranty, and there are no visual signs of any catastrophy,
    the dealer should exchnage it.


    I don't blame you for liking to live in the country. I can see your
    point. I myself have been brought up and lived in a city all my life.
    I like to visit the country often, but would not feel comfortable to
    live there full time, considering what I am used to.

    Jerry Greenberg
  20. CWatters

    CWatters Guest

    In the end the only really good insulator is distance. If lightening can arc
    from a cloud to the ground it can jump a few inches and bypass any black box
    you can invent. It just takes enough voltage.

    Having said that.... perhaps you could build something using fiber optics.
    You just need to decide how long a length of fibre you need to seperate the
    two ends of your black box. (and solve the power supply problem others have
    pointed out).
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day