Getting a Sun Ultra 5 To Work

On 26/08/2011 18:55, Tony Duell wrote: Never seen a USB-20mA (for example). Everything seems to be based on voltage thresholds these days, and the shortcomings of that were brought home to me today in discussion with a building management systems installer advising that the signaling from a leak detector would not travel several hundred feet without an (expensive) booster box at each end. We're not talking about fast baud rates here, just some remote sensing device with an output consisting of voltage-free relay contacts, feeding equipment that provides a voltage to distinguish "on" this morning from "off" this afternoon. The cable resistance has an inherent voltage drop of course, so they can't guarantee that closing the relay contacts will cause the voltage to drop sufficiently at the active equipment end. A current-sensing input could deal with that no problem, but they'd never come across the concept of current-sensing. -- Pete Peter Turnbull Network Manager University of York