Re: Reverse Logic

["Frank R. Borger_(FRB)" <frb@gammex.com>]

I've worked with German made Therapy equipment, and they never 
had anything like that. 

However, the American convention for switches, (Green is GO, Red is STOP) is in conflict with the color conventions for lamps, (Green is SAFE, Red is DANGEROUS.)

The best example I can give was a therapy linac that had a green button that was illuminated when the machine was off, (safe,) and a red button that was illuminated when the machine was operating, (dangerous.)

When you pushed the green button, its lamp turned off, and the lamp in the red button next to it  
came on. When you pushed the red button, its lamp went off and the lamp in the green button came on.

I think somebody just screwed up the switch caps or wiring during installation. I'd definitely
not want to have it operating the way it does, even if the operators were "used to it."



Frank R. Borger - Senior Physicist, Gammex RMI
fborger@gammex.com phn 608-828-7289 fax 608-828-7500

How many physicists does it take to change a light bulb?
Only one. According to Heisenberg, all you have to do
is observe the light bulb, and you change it.


>>> "Mercado, Don" <don.mercado@lmco.com> May 24, 2000 15:31 >>>
Greetings,

I just ran into a situation I've never seen before and would like your
perspective on this.

We have a German made Fein-Focus cabinet x-ray machine designed to image
components on circuit boards. The thing is computer driven, so the operator
controls most of the machine through a keyboard. On the front panel are a
red and green button with a red light between them that flashes when the
x-rays are on. The green button is labelled "ON" and the red button is
labelled "OFF". The weird thing is, when you press the red "OFF" button, it
illuminates and turns the x-rays *on*. When you press the green "ON" button,
it illuminates, turns the x-rays *off*, and the red button and flashing
light go dark. I asked the operator about this and he says that it's a
"German thing", it's addressed that way throughout the owners manual,
they're trained to do that and they're used to it now. They take it to mean
"Keep your hands OFF the machine when this button is pressed" and "Now you
can open the door and put your hands ON the parts when you press this
button." OFF turns them on and ON turns them off??? Confused the heck out of
me. 

Is there a translation problem between German and English that would account
for this? Was it assembled on our facility incorrectly? I can't believe the
FDA would let something like that pass. I'm trying to get a copy of the
manual to see how it is addressed. I'm for switching the button caps so ON
means x-rays on and OFF shuts them down.

Anyone have any experience with this machine? Any comments/suggestions would
be welcomed.

Thank you in advance.


Donald P. Mercado
Radiation Safety Officer
Lockheed Martin Space Systems, Missiles & Space - Sunnyvale Operations
O/EK-20, B/101
1111 Lockheed Martin Way
Sunnyvale, CA 94089
Ph. (408) 742-0759
Fax (408) 742-0611
Email: Don.mercado@lmco.com 

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