bob@alsys1.aecom.yu.edu (Bob Lummis) (11/29/90)
Does anyone have a recommendation for lightning protection on 10Base-T links that go through a direct-buried cable between two buildings? The buried portion of the cable is about 300 feet long. I plan to put 10Base-T transceivers at each end immediately at the building entrance points, then run the AUI cables upstairs to equipment locations. Is there some kind of thingee that I can connect between the twisted pairs and ground at each end of the cable that will short lightning-caused current surges to ground but that will not disturb 10Base-T signals? Preferably the thingees would act non-destructively (i.e. not just melt or vaporize). I think the cable TV industry uses some kind of diode-like device that does this while not interfering with TV signals. But I don't know what it is. -- Bob Lummis, Director, Research Information Technology (bob@aecom.yu.edu) Albert Einstein College of Medicine, Bronx, NY 212-430-4211 FAX:212-430-2488
kla@kampi.hut.fi (Kimmo Laaksonen) (12/11/90)
This may be the thingee you're looking for: We have an extensive terminal network at the campus based on RS422 balanced lines (2 pairs/terminal). Because RS422 is balanced the signals are all "floating" with respect to ground. To protect against static discharges etc. all long runs of cable (cables between buildings) are protected with Motorola Mozorb devices (sorry, don't remember the part number). This is a very fast semiconductor surge protection device. It's the only one I know that works against spikes fast enough. Gas discharge devices utilized by phone companies et al. aren't just that fast. The Mozorbs are bipolar, so they protect against positive & negative spikes. We connect one to each line of the pairs (that's 4/line at both ends), and ground them well. Mozorbs come in various power ratings: 600 W, 1.5 kW, and so on. I think we use the 1.5 kW variety (quite small package). Mozorbs are set to open like zeners at various voltages. I think ours are at 6.3 V, which seemed like enough. RS422 is nominally 5 V, and most receiver ICs are rated max. input voltage at c. 6 V, so we figured that'll give us enough protection. And so it seems: buildings where RS422 receivers blew during lightning storms, have caused not much trouble after Mozorbs were installed. For 10Base-T I don't know the voltages used, but they must be stated in the standard. If you think Mozorbs sound what you need, contact your local Motorola dealer for data sheets, and look up a voltage close to what the standard says (not too close, you wouldn't want the device to open in normal situations; on the other hand not too far, because then the receivers will blow before the Mozorb opens). ------------------------------------------------------------------------ Kimmo Laaksonen Internet: kla@hut.fi Helsinki University of Technology uucp: ..!mcvax!tut!santra!kla Computing Centre BITNET: KLA@FINGATE Otakaari 1, SF-02150 Espoo, Finland phone: int'l 358 0 451 4308
joem@hpgnd.grenoble.hp.com (Joe McCARTHY) (12/14/90)
/ hpgnd:comp.dcom.sys.cisco / kla@kampi.hut.fi (Kimmo Laaksonen) / 1:41 pm Dec 11, 1990 / This may be the thingee you're looking for: We have an extensive terminal network at the campus based on RS422 balanced lines (2 pairs/terminal). Because RS422 is balanced the signals are all "floating" with respect to ground. To protect against static discharges etc. all long runs of cable (cables between buildings) are protected with Motorola Mozorb devices (sorry, don't remember the part number). This is a very fast semiconductor surge protection device. It's the only one I know that works against spikes fast enough. Gas discharge devices utilized by phone companies et al. aren't just that fast. The Mozorbs are bipolar, so they protect against positive & negative spikes. We connect one to each line of the pairs (that's 4/line at both ends), and ground them well. Mozorbs come in various power ratings: 600 W, 1.5 kW, and so on. I think we use the 1.5 kW variety (quite small package). Mozorbs are set to open like zeners at various voltages. I think ours are at 6.3 V, which seemed like enough. RS422 is nominally 5 V, and most receiver ICs are rated max. input voltage at c. 6 V, so we figured that'll give us enough protection. And so it seems: buildings where RS422 receivers blew during lightning storms, have caused not much trouble after Mozorbs were installed. For 10Base-T I don't know the voltages used, but they must be stated in the standard. If you think Mozorbs sound what you need, contact your local Motorola dealer for data sheets, and look up a voltage close to what the standard says (not too close, you wouldn't want the device to open in normal situations; on the other hand not too far, because then the receivers will blow before the Mozorb opens). ------------------------------------------------------------------------ Kimmo Laaksonen Internet: kla@hut.fi Helsinki University of Technology uucp: ..!mcvax!tut!santra!kla Computing Centre BITNET: KLA@FINGATE Otakaari 1, SF-02150 Espoo, Finland phone: int'l 358 0 451 4308 ----------