On 15-May-2002 C Falconer wrote: > On Wed, 2002-05-15 at 20:54, [EMAIL PROTECTED] wrote: >> FWIW - On one industrial site I measured 70VAC between the earths of two >> buildings, but since we were using isolated differential signalling (20mA >> loop) and the opto-isolators were rated at 2.5kV isolation we didn't have >> any networking problems. > > What exactly is an opto-isolator? Is it the same as an opto-coupler?
For most practical purposes, yes. > I'm guessing that its a smallish box with two ports ( a two-port switch > if you prefer ) that has a sending light and a receiver pair twice (one > pair for TX/RX and RX/TX) so that the two sides are not electrically > connected. What is one worth? Do they need power? How much are they? > Who makes them? They come in various degrees of complexity, speed, and (of course) price. Google can probably point to specs and sources. If you're isolating sections of a LAN, fibre segments could be a good investment because they have much greater resistance to the undesirable effects of lightning than do compact isolators. Which point quite neatly swings things back to 802.11. Those putting up antennae might be wise to consider the effect of lightning on their thousands of dollars worth of sensitive interconnected computer gear. There doesn't even have to be a direct hit - the EMP and large ground potential gradient caused by a nearby strike can be surprisingly damaging. (Something I have observed first-hand.) Cheers, Brian Chatterton ( Designer of hardware for industrial data processing systems in an earlier existence :) ---------------------------------------------------------------------
