zeeff@b-tech.UUCP (Jon Zeeff) (10/05/88)
Having lost 3 modems in two lightning storms, I am suddenly interested in surge suppressors for the phone lines. I bought an inexpensive one that appears to have a small glass tube running from each line to ground. The tubes look like large diodes, except that inside they appear to have something like a resistor inside. I beefed this up by adding MOVs from each line to ground. Is this adequate protection? The modems were turned off when they were ruined - is it better to leave them on? -- Jon Zeeff Branch Technology, umix!b-tech!zeeff zeeff@b-tech.ann-arbor.mi.us
tr@wind.bellcore.com (tom reingold) (10/06/88)
Check out this month's Byte magazine. There's an article on this topic (not specific to modems). They point out that surge suppressors are not usually all that helpful. According to the article, you have to spend at least $250 to get something assuring and worthwhile. You obviously know more about circuits than I do, so your addition of MOVs to your suppressor could be adequate. I have no idea. Read the article rather than taking my understand of their conclusions seriously. Tom Reingold PAPERNET: |INTERNET: tr@bellcore.bellcore.com Bell Communications Research |UUCP-NET: bellcore!tr 445 South St room 2L350 |SOUNDNET: (201) 829-4622 [work], Morristown, NJ 07960-1910 | (201) 287-2345 [home]
henry@utzoo.uucp (Henry Spencer) (10/07/88)
In article <4789@b-tech.UUCP> zeeff@b-tech.UUCP (Jon Zeeff) writes: >Having lost 3 modems in two lightning storms, I am suddenly interested >in surge suppressors for the phone lines. I bought an inexpensive one >that appears to have a small glass tube running from each line to >ground. The tubes look like large diodes, except that inside they >appear to have something like a resistor inside. I beefed this up by >adding MOVs from each line to ground. This isn't necessarily a good idea. Protecting phone lines is much trickier than protecting power, because phone lines have to meet fairly strict electrical specs or you will have trouble, either equipment failure or nasty mail from the phone company. For example, I trust your MOVs are rated for a nice high voltage (ringing voltages are *not* low) and have quite low leakage currents at normal voltages (so the phone company doesn't conclude that there's an equipment fault somewhere)? I would not recommend adding components yourself unless you have checked specs carefully and know what you're doing. -- The meek can have the Earth; | Henry Spencer at U of Toronto Zoology the rest of us have other plans.|uunet!attcan!utzoo!henry henry@zoo.toronto.edu
richman@uxe.cso.uiuc.edu (10/07/88)
We have had this problem repeatedly at my workplace. One easy
and effective method to avoid the problem is to unhook the RS232
connector after you are finished with your remote session. Very
inexpensive. We also looked into more sophisticated versions of
surge protectors and found out that they (i) were not all that
useful, (ii) their usefulness was a function of how close to your
modem the lightning struck and (iii) if one of these devices took
a fairly strong surge, the suppression device would be damaged and
the cost of repair might exceed the cost of the modem. Therefore,
we opted for the sure method. Maybe technology has improved over
the past 12 months since we looked into this, though. Good luck.
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Mike Richman
internet: richman@uxe.cso.uiuc.edu
bitnet: richman%uxe.cso.uiuc.edu@uiucvmd
uucp: {puree,convex,uunet,...}!uiucuxc!uxe!richman
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=