Thanks for the repeater mod help from my other thread. Here is a new challenging task given by me. i am using a hanger (like a hook) to hang a key. How can i make switch or any solutions that i can achieve below procedure: 1) a key hanging to the hook will open the circuit. 2)When anyone remove the key, it will closed circuit(complete circuit) and my transmitter will be activated. 3) here is what i am stuck with since i have closed the switch, the transmitter will keep on transmitting thereby wasting power UNTIL i return the key. how can i open up the circuit again WITHOUT hanging back the key. 4) Key returns and it STILL a open circuit and back to step 1. Any method/ solution are welcome. If your answer is a pressure switch, please explain me how it works. i have never use it before. Thanks a lot.