Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!rpi!uupsi!ccavax!bruce From: bruce@ccavax.camb.com (Barton F. Bruce) Newsgroups: comp.dcom.lans Subject: Re: Lightning Protection Message-ID: <38200.275af66f@ccavax.camb.com> Date: 4 Dec 90 05:05:51 GMT References: <403@alsys1.aecom.yu.edu> Organization: Cambridge Computer Associates, Inc. Lines: 84 In article <403@alsys1.aecom.yu.edu>, bob@alsys1.aecom.yu.edu (Bob Lummis) writes: > In a previous posting I asked for information on how to protect direct- > buried copper cable from lightning and still be able to use it for 10base-T. As long as you simply want an answer to your question... This is NOT a recommendation. AS others have pointed out, you are doing a 'NO-NO'. Old carbon gap type arrestors are generally being replaced by gas tube devices that don't develop carbon dust noise as the the years go by. Even better, the 3 electrode gas tubes clamp both sides of the line and ground together simultaneously if any 2 of the electrodes arc. Gas tubes can absorb a lot of energy, but are not as fast as some weaker diodes. The diodes alone would get smoked pretty quickly. Used together, you get the best of both. Another type of protection often included in CO or building entrance protectors is called a 'heat-coil'. This is a relatively slow acting mechanism to protect from fires caused by high current low voltage problems such as power line crosses to 110v which is to low to fire normal protectors (which have to pass ringing superimposed on 48vdc). Such a power line cross must be cleared before the cooking relatively small guage wire becomes a fire hazzard. The protectors at the subscriber end of the wire are more to protect people, and may well let equipment get zapped. Some of the newer 3 electrode gas tube subscriber arrestors might be what you want, but the CO grade plug in modules are best. You should have this class protection on ALL pairs entering each building, not just for this application. The blocks that take these plug in arrestors come in 100 pair, 25 pair, 10, and even 6 pair configurations. Some have long stub cables to splice into larger cables at the entrance of each CO. The other side of that type of block might well be wire wrap tails. In the smaller sizes, they may look like '66' punch blocks and have various combinations of punch, tail, and RJ21x (25 pair amphenol 'telco' connector) in and/or out. The CO grade arrestor world is split in two. Reliable, NTI, ATT, Cook (well they are NTI, now), and Porta Systems all make interchangable modules with gold MALE pins protruding from each plug in module. They all fit each other's blocks. Porta Systems also has their own desing that is a tad cheaper. It has tin plated round FEMALE holes that plug onto square MALE protruding pins in the base block. I only go into this detail because I LIKE Porta SysteM's premium module (the Delta series). It is available to fit the 'other' style blocks, but if you order their blocks, you will have to use their modules (no big deal, as long as you order the right pieces). The Delta modules have 3 electrode gas tubes, diodes, and heat coils, and backup air gaps all in one package. I think the heat coils are used by folks using T1 (1.544 mhz) and probably T2 (~2 x T1), but I wonder if the heat coil has any signifucant impedence at enet speed. Ask. There is more than one type of heat coil available in the modules, and, though the normal nominal voltage of 230 is what you will get by default (to not fire with ringing + 48vdc) and is #95BCDXN-230, there are several LOWER or even HIGHER standard voltages available. You probably want the LOWEST they offer. If you are ysing the same cable for other services, try to get some of the optional colors for different voltages. Often RED modules are the normal voltage, but are reserved for 'special' ckts. The plug in modules are also available in carbon block, and 2 electrode styles as well as only heat coil, or only sneak current fuse, as well as straight through specials for high voltage testing. You can terminate different pairs as you please. The carbon modules are well under $2, the Delta(tm) modules are up near $9 each. There are many possibilities in between. If you have 10s of thousands of these in each of hundreds of COs, you worry about what you specify. With your project, I would go for the 'good' stuff. An empty 10 pair block that is 66 type punch in and out probably costs $25. If you are getting literature from Porta Systems, ask for their stuff that describes deploying heat-coil and sneak-current fuses at appropriate ends of inside plant, as well as whatever they have on lightning protection. Porta Systems in in Soyosett (sp?) NY. If you just want home entrance grade one or few pair blocks, try TII Industries in Farmingdale (also NY), but this is hardly the same class stuff. BTW the ground on the block needs to get to a good quality ground as close by as possible. There are pages that can be written about that connection, but I am going to stop here.