INPUT>Output-Monitor

--=========================================================================================================
--DoNot remove this Credits
--Created On 19th MARCH 2014
--by Angel_Code http://www.computercraft.info/forums2/index.php?/user/18955-angel-code/
--Support Provided By theoriginalbit http://computercraft.theoriginalbit.com/
--Support Provided By Bomb Bloke http://www.computercraft.info/forums2/index.php?/user/15121-bomb-bloke/
--=========================================================================================================
Mon = peripheral.wrap("top")  --Change "top" to the side the monitor is on.
local function centerText(text)
  x,y = Mon.getSize()
  x1,y1 = Mon.getCursorPos()
  Mon.setCursorPos((math.floor(x/2) - (math.floor(#text/2))), y1)
  Mon.write(text)
end

local function defence()
    Mon.clear()
    Mon.setCursorPos(1, 1)
    centerText("=========================================")
    Mon.setCursorPos(1, 2)
    centerText("WARNING!")
    Mon.setCursorPos(1, 3)
    centerText("INCOMING MISSILE")
    Mon.setCursorPos(1, 4)
    centerText("ACTIVATING FORCEFIELD")
    redstone.setOutput("right", true) --Change "right" to the OUTPUT side.
    Mon.setCursorPos(1, 6)
    centerText("=========================================")

    local count = 60 -- Change 60 to the amout of time in seconds a redstone signal should be turned on for.
while true do
  Mon.setCursorPos(1, 5)
  centerText("Field Active For " ..count.. " Seconds")
  sleep(0.5)
  count = count - 1
  if count < 0 then
    redstone.setOutput("right", false) --Change "right" to the OUTPUT side.
    Mon.clear()
    check()
  end
end
end

function check()
 while true do
   if redstone.getInput("left") then defence() end  -- Change "left" to the INPUT side.
      os.pullEvent("redstone")
   end
end

check()