Two hand no tie down cycle start system

I am currently enrolled at Alexandria Tech for fluid power in MN. Im having trouble in a plc class useing logixpro 500.
My teacher wants me to make a plc logic with a two-hand no tie down cycle-start system. Which means two push buttons pushed at the same time to start the program. Now the kicker is that if one push button is activated or tied down in the work position the program will not start. My teacher wants me to stay away from timers in this ladder of logic.
I was hoping you could send me a hint or some feedback on how to solve my problem
thanks richard

Richard

This subject has been covered before, so rather than repeat what has been said and try and claim it as my own work, here is a link to a thread discussing this subject.

In this thread Terry Woods gives a detailed explanation into anti-tiedown methods, so the credit will go to Terry and any others who contributed to this and other threads dealing with this subject.

For more threads just search this site for 'anti-tiedown'

Paul

Im not real sure what code may require for this but we have banner DUO TOUCH start buttons and safety relays.
http://www.bannerengineering.com/products/machine_safety/duotouch/

After reading all the post in the above link I think this is the only way to go.

Bob

Thanks.
paul the hyperlink was just what i wanted and it
worked out great for me.
richard