Good attempt.  Good exercise.

John


--- Marcel Birthelmer <marcelb.lists@gmail.com> wrote:

> Hi all,
> I'm sure to most of you this will be boring, but
> this circuit
> represents the first time I've come up with a
> useful, non-trivial,
> functional analog(ish) circuit, so I'd like to share
> it with the
> group. Circuit is attached, or available at
> http://marcel.carrietech.com/switches.png
> 
>  There are three switches mapped to two outputs. SW1
> = 01, SW2 = 10,
> SW3=11. The idea of this circuit was to prevent SW1
> and SW2 being
> pressed at the same time to cause the output to look
> like SW3. (If SW3
> is pressed along with either of the other two, the
> output will be 11.)
> 
>  In the idle state, both voltages are low. When one
> switch (assume
> it's SW1, without loss of generality) is closed, the
> transistor Q2
> turns on, dropping its collector voltage (and thus
> Q3's base voltage)
> close to 0. Q3, in turn, is cut off, leaving no
> current to flow
> through SW2 if it is closed. The same takes place if
> SW2 is pressed
> first. When SW3 is closed, both outputs are forced
> high via the
> diodes.
> 
> Any comments are welcome.
> Thanks,
> - Marcel
> > -- 
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
> 



 
____________________________________________________________________________________
Cheap talk?
Check out Yahoo! Messenger's low PC-to-Phone call rates.
http://voice.yahoo.com
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist