Minecraft>BaseRepeater

rednet.open("left")
rednet.open("right")

while true do
        event, id, text = os.pullEvent()
        if event == "rednet_message" then
        if id == 24 then
            rednet.close("right")
            rednet.send(20, text)
            rednet.open("right")
        elseif id == 20 then
            rednet.close("left")
            rednet.send(24, text)
            rednet.open("left")
        end
        end
end