startup.lua

local chat = peripheral.find "chat_box"
local side = "right"
local onoff = false

chat.setName "Tesla Thingy"

function set()
    redstone.setOutput(side, onoff)
end

while true do
    _, _, usr, msg = os.pullEvent "chat_message"

    local cmd = string.sub(msg, 2)

    print(usr, msg, cmd)

    if cmd == "tesla" then
        onoff = not onoff
        chat.say("Acknowledged. RS: " .. tostring(onoff))
        set()
    end
end