I need to read some switch closures with PICs in a ship.  The cables
running to the switches will run several hundred feet and will be run
alongside AC power lines and possibly some lines to big motors.  There
will be three PIC circuits in three different locations reading the
switches.  They will be daisy chained.  There won't be any serial coms
between the pics, just 11 switch lines and common.  There won't be any
fast switching, just going to alarm contacts on doors.

Any suggestions for protecting the pics and keeping noise on the lines
from looking like switch closures?

Also, should I use 5V going to the closures or bump it up to 12 or 24
and step it down with a zeener at the pic end for better noise immunity?