test

function controlled()
while true do
local modem = peripheral.wrap("top")
modem.open(3)
local event, modemSide, senderChannel, replyChannel, message, senderDistance = os.pullEvent("modem_message")
if "a" == message  then
rs.setOutput("back", true)
sleep(1)
rs.setOutput("back", false)
end
end
end

return controlled()