A 12v trigger works with an electric screen or a reciever if I am not mistaken. The screen, receiver or other device has to have a 12v connector and you plug a cable between the projector and the device. When the projector is turned on, the device it is plugged into would also be turned on. So for instance, if you have the projector and electric screen connected, when you turn on the projector the screen would roll down.