On Friday 15 February 2002 10:24, alta wrote:
Malcom ...
Good find. I am sending a copy to TrippLite Tech Support for verification. Unlike the previous web site, the cable depicted at the following web site (you provided) seems to match my measurements, and the documentation for genericups 5.
http://www.exploits.org/nut/library/tripplite.html
The ups software changes the RTS line pin-7 to +12v, and leaves DTR line pin-4 at -12v. Yet the diagram says +V. So, not everything adds up for me.
To a computer person, the pin-assignments on the TrippLite (and other UPS units) and associated cables seem rather odd -- evidently not designed by a computer hardware person. But then, the computer hardware designers did not use pin-1 as ground, which is an unwritten electronic standard.
Actually, they did. On the 25 pin connector, pin 1 is ground, but it is frame ground. Signal ground is separate, and is on pin 7. When IBM decided to use a nine pin connector, they had to decide which of the 25 pin connector's signals they could do without. Among others, they dropped frame ground while retaining signal ground. Since signal ground is not always the same as frame ground, it would have been inappropriate to assign it to pin 1. BTW, Tripplite could easily have put those resistors and the diode inside their unit. Of course that would have cost them a few cents more per unit in manufacturing costs--and they wouldn't be able to sell high priced shutdown cables. If I ever do hook my UPSes up, I'll open 'em up and add the components inside if it's at all feasible. Then I'll just use a standard 9 pin extension cable. -- Regards, Malcolm KMail l.3.1 -- KDE 2.2.2 -- SuSE Linux 7.3 Remove the dots to email me