1st signal control

--First computer on the line ID 183 with a wired modem on the top
rednet.open("top")
while true do
	local left=rs.getInput("left")
	local right=rs.getInput("right")
	local senderID,message,protocol=rednet.receive(1)
	if left then
		os.startTimer(3)
		exit = false
		while not exit do
			event = os.pullEvent()
			if event =="timer" then
				exit = true
			elseif event=="redstone" then
				local right = rs.getInput("right")
				if right then rs.setOutput("front",true)
					rs.setOutput("back",true)
					rednet.send(202,"blocked")
					exit = true
				end
			end
		end
 	elseif right then
		os.startTimer(3)
		exit = false
		while not exit do
			event = os.pullEvent()
			if event =="timer" then
				exit = true
			elseif event=="redstone" then
				local left= rs.getInput("left")
				if left then
					rs.setOutput("front",true)
					rs.setOutput("back",true)
					rednet.send(202,"clear")
					exit = true
				end
			end
		end
	end
	if message=="clear" then
		rs.setOutput("front",false)
		rs.setOutput("back",false)
	elseif message=="blocked" then
	 	rs.setOutput("front",true)
		rs.setOutput("back",true)
end