Wafer use *frequency spectrum ranges between 300-500 MHz and most of the transmitter/receivers rely on hopping or rolling code technology. This approach prevents perpetrators from recording a code and replaying it to open a garage door or automatic sliding door. Since the signal is supposed to be significantly different from that of any other garage door remote control, WAFER claim it is impossible for someone other than the owner of the remote to open the door. When the transmitter sends a code, it generates a new code using an encoder. The receiver, after receiving a correct code, uses the same encoder with the same original seed to generate a new code that it will not be accepted in the next time.