DSU/CSU Electrical Protection

Discussion in 'Cisco' started by James, Jun 10, 2004.

  1. James

    James Guest

    We are having problems with the internal cisco DSU/CSU cards on cisco
    1721s as they are dying. I'm guessing this is due to energy surges,
    such as lighting and induced voltages.

    I cannot seem to find any optical isolation equipment, which would
    work. Opto isolation is the best, in my experience. Any
    recommendations on opto isolation are appreciated.

    What I have found, at www.edcosurge.com/products/telecom/lcpd.asp
    is RJ45 surge protection. It operates (clamps) at 8, 15 and 30 volts.
    Any recommendations on which volatage to select? Other circuits or
    devices for DSU/CSU protection?

    The circuits are Verizon 56kbps Frame Relay, if that matters....

    Any discussion or recommendations are most welcome.

    James, Jun 10, 2004
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  2. James

    w_tom Guest

    If your problem is due to environmental transients, then
    nothing is going to stop block, or absorb those transients.
    However we routinely avoid such damage by doing what Ben
    Franklin did in 1752 to protect church steeples. Concepts are
    that simple and that well proven.

    Destructive transients are current sources. Therefore
    voltage will increase, as necessary, to maintain that current
    flow. Miles of non-conductive air did not stop that
    transient. Is a silly quarter inch of opto-isolation going to
    do what miles of air could not? That is exactly what myth
    purveyors would have you believe when they promote their
    ineffective and grossly overpriced protectors.

    The concepts are posted in previous discussions:
    "RJ-11 line protection?" on 31 Dec 2003 in pdx.computing at
    "strange problem after power surge/thunderstorm" in
    comp.dcom.modems on 31 Mar 2003 at
    "surge protectors trip Ground Fault Breaker" in
    alt.engineering.electrical on 28 Aug 2003 at

    If running a serious communication facility, then your
    building should be properly wired for effective transient
    protection. That means earthing all incoming wires per post
    1990 NEC requirements - all wires connect to single point
    earth ground either by direct hardwire or via a protector.
    That also means exceeding those NEC requirements. Concepts of
    earthing discussed among engineers in the newsgroup
    Storm and Lightning damage in the country 28 Jul 2002
    Lightning Nightmares!! 10 Aug 2002
    http://tinyurl.com/ghgv and http://tinyurl.com/ghgm

    Destructive transients occur typically once every eight
    years. The frequency of your problems suggest that your
    building even violates NEC requirements for human safety - a
    problem more serious than lightning. Transistors being
    damaged because the building even may have human safety
    issues. You have much to read. Both human safety and
    transistor safety issues involve the single point earth
    w_tom, Jun 10, 2004
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  3. James

    James Guest

    Fast acting devices, in the order of 10s or hundreds of nano-seconds,
    sense voltage increase to trigger. By the time the increase current is
    actually flowing at a given point, it's too lated to protect the
    communications interfaces, even thougth the duration of the increase
    current flow is of the order of nano seconds.
    No body is talking about stopping the brunt of a lighting induced surge.
    What we are talking about is filtering, clamping and diverting the
    increased energy under the curve for nano seconds that is at a higer
    voltage. If the voltage never surges, then the device only draws the
    current it needs or can handle.

    Um, we seem to be speaking different dialects here. Our facilities
    are all code compliant, and the incomming signal wire is burried
    (mostly) but it is the property of Verizon.
    I would only use opto isolation inside where the engergy surges are
    actually occuring in and on the skin of the wire (i.e. inside of the
    plastic insulation that wraps the wire.

    I do appreciate your links, but, I assure you code compliance, even
    the useful things in NEC 2004 are not at issue. We are in the
    lightning capital of the world (Tampabay) and our customer has many
    facilities, some that criss cross swamps and forest, so they are
    natural settings for all sorts of induced energy surges. And yes we
    have areas where the ground is a very poor conductor, but, we 'ohn'
    out all of our ground resistances, and install mitigation equipment,
    like triads, as necessary.
    This would be useful, except the 'gas-discharge' surge protectors used
    by telcos are too slow, the clamp in the order of milli seconds.
    This article is irrelevant. The POTS (plain old telephone service)
    allows 90 volts to activate the ringer, so if you clamped at 95 volts
    you still allow a large amount of energy into the POTS interface.
    The 4 wire or 2 wire copper circuit thats in terminated in the Telcos
    RJ4ks connector surely does not swing 90Vp-p.

    Any idea what the maximum voltage swing is on a Frame RElay circuit
    on 4 wire copper? That would be useful information.
    OK, now you are talking about energy surges on the power input feed.
    This is not the problem. The cisco routers are fine, we keep loosing
    the internal 56K dsu/csu cards. Therefore the surges are comming in on
    the 4-wire copper data circuit. Besides the routers are behing UPSes
    that have 'ferro-resonant' transformers. Ferro-Resonant tranformers do
    indeed block the energy surges on power feeds. You should read up on
    those devices.......

    When I build datacenters, all power feeds are behind 1:1
    ferro-resonant transformers for protections. This is not the problem.
    Dude, the problem is not on the power feed. I routinely consult to
    power utilities on power quality issues.....
    This statistic is utter BULLSHIT. I can show you facilities that are
    lightning proned, multiple times a year, no matter what you do. Other
    facilities less than a mile away, never get hit. It's due to a complex
    set of environmental issue, mostly realted to conductivity of the
    soils and the surrounding structures and trees...
    You, are full of shit!
    James, Jun 10, 2004
  4. James

    w_tom Guest

    You are making wild assumptions. For example code
    compliance means the building does not kill humans. Code
    compliant building can still kill transistors. Furthermore,
    it does not matter whether wire is buried or overhead - as you
    should have well known. Either way, incoming wire can conduct
    destructive surges directly into equipment as was well
    understood long before WWII.

    Your technical background is so based upon urban myths that
    you even believed that outright distortion about gas discharge
    tubes (GDTs) taking milliseconds to response. I thought that
    fairy tale had died long ago. If true, then those 30
    microsecond transients were never diverted by the GDT. So how
    did GDTs provide protection routinely so many decades ago?
    Funny thing about numbers. They expose junk science such as
    GDTs take milliseconds to respond.

    Of course, you did not suffer damage because a transient
    incoming on telephone line had no outgoing path - therefore
    damage could not exist. You do remember your elementary
    school science lesson. Without both an incoming and outgoing
    path, then no electric current - and therefore no damage. So
    what was the incoming and outgoing electrical path so
    necessary for damage to occur? Did you first ask that
    question? Or did you assume electricity comes in on phone
    line, damages line card, then stops? In the meantime, telco
    would have already installed effective protection on its
    incoming wires. (Verizon does not install wires in Tampa Bay
    - which you obviously knew). Protection that would be only as
    effective as the earth ground your building has provided.
    Earthing that is well beyond what any code requirement calls
    for. You did know about this single point earth ground
    requirement - right? This is also why electronics connected
    to phone lines are so easily damaged by AC electric

    Then there is the silly myth that ferro-reasonant UPSes will
    stop transients. Did you notice the breakdown voltage?
    Cisco power supply already provides protection meaning a
    plug-in UPS provided no additional protection - once basic
    electric principles and the numerical specifications are

    You have damage because you have not learned about effective
    protection. You actually think a filter is going to 'blunt'
    the energy of a transient? Only in your dreams. First apply
    real world numbers. Its called breakdown voltage which makes
    your speculations irrelevant. Anything that the optocoupler
    or filter was going to accomplish is available in that Cisco
    interface card. Why do you think the protectors you seek are
    not readily available?

    You want better protection? Put knots in the wires. That
    too is a classic urban myth.

    A plug-in UPS only provides the transient with more
    destructive paths through your Cisco. That UPS does not even
    claim to protect from the type of transient that typically
    damages electronics. You did not bother to read what has been
    proven by generations of experience, is well published in IEEE
    publications, and would not be understood by the mentally meek
    among us who use "Dude" to mask their ignorance. This
    sentence completely justified by your insults as well as your
    responses that are so classic of scam artist promotions.

    If you want help - and your technically naive responses
    explain why you had damage - then start by being civil and by
    learning about things you only have "Dude" knowledge of -
    better known as junk science. Yes, in your responses were a
    few technically correct gems alongside old wive's tales.

    You are trained by so many myths as to even think telcos
    used gas discharge tubes? GDTs were obsoleted by a low
    capacitance type of MOV which is turn was obsoleted by a
    semiconductor type device. Anyone with telco knowledge would
    have known this. You have much to learn and have been brain
    washed by too many junk science legends.

    You are having problems with the Cisco because you do not
    have effective protection - a problem directly traceable to
    human ignorance and some mythical belief that those plug-in
    UPSes provide that protection. Even worse, you actually think
    that a code compliant building provides effective transistor
    protection? Where did that wild assumption come from? We still
    build new buildings as if the transistor did not exist.

    You cannot find that protector because it does not exist for
    good reasons. Same protection already exists inside the
    Cisco. You have even fallen for the classic myth that a
    plug-in UPS provided protection - when even the manufacturer
    does not make that claim. Post the long list of
    manufacturer's numerical specs if you think otherwise. But
    good luck finding those specs. Only one of us does not
    worship urban myths and then insult the other. You want
    help. Then learn how much you don't know and then be civil.
    Even the typical average of one destructive transient every
    eight years was accurate - had you only read the cited
    material rather than declare you have all the answers.
    w_tom, Jun 11, 2004
  5. James

    James Guest

    w_tom wrote:


    You have a really bad attitude. I'm looking for help,
    not somebody who still thinks the problem in in the power circuitry.
    It's not in the power circuits, it's in the data circuits or the
    DSU/CSU design that cisco uses on the internal cards.
    If it was on the power feed circuits, we'd have problems with the
    cisco routers, there is no problem there. We have put power quality
    meters all over the power feeds... NO problems.

    I not looking for a lecture (and you are wrong and awefully
    presumptive, that why I said you are full of shit, you presume to know
    the environment and you don't. You have not listend to the statements
    either. Verizon has had equipment blowouts too, even with the precious
    gas-discharge device you think are wonderful and fast acting. I' sure
    there are gas discharge protection that is better, than the vintage
    wwII stuff you seem to have kindred emotions with, but, it does not
    clamp, act, divert or filter in a fast enough time to be useful for
    many transients. You need devices that act between 10 and 100 nano
    seconds. I use devices such as spectrum and network analzers for Rf
    problems. I was hoping somebody would suggest a test set, such as
    ameritech, that would catch this problem, so I do not have to lugg
    100,000.00 worth of lab gear out into the field....

    If you are not going to make useful suggestions, then please find some
    body else to harrass. POWER QUALITY IS NOT THE PROBOLEM! It's
    intermittant energy on the copper 4-wire circuit. Also, I have already
    found lots of information that suggests the problem is indeed in the
    cisco dsu/csu design on those cards. This is reinforced by the fact
    that now, the dsu/csu devices are locking up at other facilities that
    are not on extended demarcs. These internal dsu/csu that cisco has on
    the card are indeed a poor design, and probable left over form one of
    the many companies that cisco has pruchased.

    I now have intermittant failure, the circuit quits working and the rx
    light goes out at 4 out of 22 sites with cisco 1721 all with internal
    dsu/csu cards from cisco. As soon as a technician cycles power on the
    cisco 1721, it starts woring again. One dsu/csu card has failed
    completely. 2/4 intermittant sites have the VERISON smart jack within
    our facility, so the problem(s) are at least partially due to
    something not related to the extended demarc issue.

    Please try to focus on what I'm saying and be helpful,
    non-presumptive, and polite, or go away. Your choice.

    Your wasting a lot of bandwidth on power feed issues that are
    irrelevant to by issues.....

    PS you are right about one thing, I did not discuss filter capacitors
    with ferro-resonant transformers, as they are usually understood to be
    part of circuit protection, that is built into the better ups. And
    that's the point, WE should not assume to know about thing that the
    author has not written about in the email. It's not a power quality
    problem. It's a problem with trasients on the copper data circuit,
    and a poor internal dsu/csu design/implementation on cisco's part.

    What I was looking for from the readers of this list is helpful
    suggestions, such as:

    Or any other protection/monitoring/logging equipment to document the
    problem. OR better yet IOS commands with will capture, log, and
    forwared electrical signals or layer 1 problems so as to document the
    short comings of Verizon.

    It's been suggested that Paradyne's top of the line external dsu/csu
    has some excellent circuitry for capturing data on transient
    electrical problems...

    PS, I have friends in cisco engineering that will eventually come
    clean on these issues, after I email then waveforms of the culprit...

    James, Jun 11, 2004
  6. James

    w_tom Guest

    The tone of my post changed only after you starting
    insulting AND posting classic urban myths as if fact. Your
    ferro-reasonant, plug-in UPSes as effective transient
    protection is classic myth. If the problem is on all Cisco
    cards, then you have plenty of 'dead bodies' to identify the
    incoming and outgoing path of failure. We learned thirty
    years ago why phone line damage is most often incoming on AC
    mains. But then as engineers, we first had to see facts
    opinions could exist.

    You started the attitude "Dude". Now decide whether you
    want learn or want to promote more urban myths. Line cards
    must be designed to withstand 1000 volt transients. That is
    even FCC requirement (I believe Part 68). Those Cisco cards
    should not be damaged IF the building is properly constructed
    and wired.

    Meanwhile, describe how the extended demarcs are installed -
    location, distance from single point earth ground, how and
    what earthing wire is routed through, distance to Cisco line
    cards, etc. Everything, including the wire, is an electronic
    component of that circuit.

    First place one starts when suffering transient damage is
    the single point earth ground. Measurements are not
    sufficient. Visual inspection is required. As Polyphaser
    demonstrates, if all incoming utilities don't share the same
    single point earth ground, then damage results to electronics
    with sufficient internal protection. The electronics becomes
    a preferred path of those transients. Again, read the
    citations before responding. This Polyphaser app note
    demonstrates how transients enter on buried phone line.
    Remember that buried line that you claimed would not carry
    destructive transients? Experts say otherwise:

    All equipment connected to phone lines has onboard
    protection. Protection that is sufficient but will be
    overwhelmed when a building is not constructed / enhanced to
    meet minimally acceptable requirements. Those Cisco cards are
    not routinely failing for other customers. Building wide
    problems may be insolvable without first learning about what
    was posted in those previous posts. That means you cannot
    dismiss the concepts until you have first read what was
    learned and demonstrated by generations of theory, papers, and
    experience. Polyphaser also demonstrates the problem in
    simple terms:
    If you thought a code compliant building accomplished this,
    they you are now ready for an expensive lesson in transient
    protection and the all so critical single point earth ground.

    If the problem is incoming on copper data circuits, then
    where is the outgoing path? No outgoing path means no damage.
    And how is that transient being completely ignored by the
    'telco provided' protection that exists where phone lines
    enter your building? Why could you have destructive
    transients on phone line if those lines already have telco
    installed protection? It was answered previously. Maybe you
    could provide a better reason. Visual inspection provides
    important facts.
    w_tom, Jun 11, 2004
  7. James

    Lex Ein Guest

    The usual advice from experience (boilerplate with slight editing for
    your situation):
    - Consult Verizon to run full diagnostics/ send a tech. There may be a
    wiring fault which is killing the equipment.
    - Consult Verizon to guarantee that there's no chance of ringing voltage
    on the pair(s).
    - Consult Verizon to guarantee that they're not performing ANY overnight
    automatic diagnostic testing on the pair(s).
    - Consult your network installation contractors about this issue. They
    may be able to test for a wiring fault sooner than Verizon.
    - Consult Cisco about Cisco-approved DSU/CSU protection products.
    - Make sure Cisco is replacing the failing equipment under warranty, and
    with "advance RMA" until the problem is resolved.
    - Test for voltage & current transients, ground faults and AC
    overvoltage, especially during building heating/ventilation/air
    conditioning cycling and lighting transitions.
    - Verify the 1721 power supply is solid (low noise, not fading, spiking,
    no leakage current, no imposed AC or switching noise).
    - Verify the wiring in the building, and in the equipment closet (no
    hot/neutral swap, valid ground, <0.1V between ground points throughout
    - If your equipment is plugged into a GFI/GFCI, try a non-GFI outlet.
    GFIs fail over time, I found out.
    - Try an Edco device. Consult Verizon to specify 8V, 15V, or 30V
    protection, or just measure the voltage across your telco pair(s), and
    get the Edco device with the next higher voltage rating. If you measure
    6V, get the 8V protection. Make very sure this device is grounded to a
    valid non-structural building ground (all copper water pipe), same as
    all the other network equipment.
    - Make sure the cleaning crew isn't plugging their 12-horsepower vacuums
    and floor polishers into the same circuit as your network gear.

    Normally, telco-connected gear is well protected against the usual

    And finally, don't exclude the possibility that Cisco may have a chronic
    problem with this module, especially if it's a low-demand device.

    Good luck.
    Lex Ein, Jun 14, 2004
  8. James

    James Guest

    They are getting the package distroyed in one location, twice by
    lightning. They are trying,but I'm going to get some test gear and do
    some monitoring on the circuits myself. Any recommendations on
    test_set? Ameritech seems to be the most recommended for deep analysis..

    All of these are Verizons domain. I'm looking for tests and test
    equipment I can use, in addition to Verizon.
    power feed transients are not the problem. The routers stay up
    and never fail. After a storm the internal dsu (WIC-1dsu-56k4) says
    that serial is up, line protocol is down. Cycle power on the router
    (and hence on the internal dsu/csu) and serial comes up, line protocol
    {Frame Relay} comes up, and everything is fine. It could be the
    embedded RTOS (i.e. ios) filling up a error file buffer, but, cisco
    uses circuit writes to avoid locking up a device on error messages....

    Any IOS suggestions or things to check?
    Searching the net for "WIC-1dsu-56k4" reveals lots of refurbished
    cards. NOt many used cards. This and other data lead me to believe
    it a less than robust internal dsu/csu implementation. They have
    deprecated the sister t1 card, which it's replacement now does
    single channel 64/56k with the internal dsu/csu.....
    Power is not the problem and I have put power quality metering/logging
    equipment on site for days, and during lightning storms. No problems,
    transients or other isses that the equipment does not handle.

    Comm circuits in on a separate grounding system. It does not make much
    sense to ground signaling devices to the same grounds that 480v 3
    phase systems use, in my experience...... 3 phase power protections
    schemes are much more robust than 110V single phase stuff most
    networkers uses......
    Now you are talking. We have devices coming form LEA, Edco, and
    Telebyte... Any other suggestions, before I desing something myself?

    see above
    Yep, as soon as I have some log files and waveforms, I'm going to
    email them to some 'assholes' I know personnally inside of cisco.
    Cisco use to be a premiere technical company. Now they are like
    microsoft, not owning up to technical flaws.

    Oh well, my customer is now letting me design networking system from
    the ground floor up. Cisco was pushed on us, an industrial
    environment, by the MIS dir at a gov agnecy. Now I have about 15
    different issue that let me plan on system enchancements without using
    cisco gear.....

    Now I'm happy, and did not even have to get into extended temperature
    issue, as those are coming.....

    James, Jun 15, 2004
  9. James

    Lex Ein Guest

    Since you mention actual lightning damage (that wasn't clear before),
    the best approach is a spark gap+snubber+fuse chain with a good ground.
    It once was usual for the telco to spark-gap and fuse every pair
    coming into a building, to a really good ground. This should be
    inspected and tested. This knocks down the likely voltage excursion to
    200-1000 volts (ringing voltage is still 90-140 pulsed DC), leaving the
    end equipment to fend for itself.
    The Edco devices sound good, if they recover without shorting or
    degrading their signal characteristics.

    But if there's no upstream protection, the Edco probably won't be able
    to sustain the damage or protect the DSU/CSU.

    Sorry, no advice to offer on brands/models of testing gear.
    Lex Ein, Jun 16, 2004
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