US Patent 7106170 Garage door opener

A garage door opener comprises at least two radio frequency transmitters, a radio frequency receiver, at least two memories, and a processor. Each memory corresponds to one radio frequency transmitter and stores a code of a corresponding radio frequency transmitter. The radio frequency transmitter is connected to the processor by electrical connectors. It is impossible to mis-study to the other radio frequency transmitter because the processor in the host computer has no program mode. Since each memory corresponds to one radio frequency transmitter, when one radio frequency transmitter is lost, a corresponding memory is eliminated to make the lost radio frequency transmitter disuse.