The first wireless garage door openers were invented and developed by two American inventors at the same time, one in Illinois and the other in Washington state. They were strangers to each other.[4].
First Stage: The first garage door opener remote controls were simple and consisted of a simple transmitter (the remote) and a receiver that controlled the opening mechanism. The transmitter would transmit on a designated frequency; The receiver would listen to the radio signal, then open or close the garage, depending on the position of the door. The basic concept of this dates back to World War II. This type of system was used to detonate remote bombs. While novel at the time, the technology continued its course when garage door openers became widely available and used. So, a person not only opened their garage door, they also opened their neighbor's garage door. While the garage door remote control has low power and range, it was powerful enough to interfere with other receivers in the area.
Second stage: The wireless garage door opener system took care of the frequency sharing problem. To rectify this, multi-code systems were developed. These systems require a garage door owner to preset a digital code by changing eight to twelve DIP switches on the receiver and transmitter. While these switches provided garage door systems with 2=256 to 2=4,096 different codes, they were not designed with high security in mind; the main intention was to avoid interference with similar systems nearby. Criminals were able to defeat the basic security of this system by trying different codes on a regular transmitter. They could also make code grabbers to record and retransmit a signal, or code scanners, which would try all possible combinations in a short period of time. Multi-code drives became unpopular in areas where security was an issue, but because of their ease of programming, such openers are often used to operate things such as gates in gated apartment complexes.
An intermediate stage of the garage door opener market between the second and third stages eliminated DIP switches and used remote controls preprogrammed to one of approximately 3.5 billion unique codes. This system was backward compatible with DIP switch remote codes, and each remote code (either with DIP switches or a unique pre-programmed code) can be added to the receiver's memory by pressing the learn button on the automation, and can be removed from the receiver's memory by holding it. While the code transmitted by the remote was still fixed, it could not be changed by the user (except if using legacy DIP switch remotes) and was much more difficult to duplicate unless two remotes shared the same code (which was highly unlikely since of two remotes sharing the same code it was 1 in 3.5 billion, unless using legacy DIP switch remotes). This approach was an improvement over fixed DIP switching codes, but soon became obsolete when rolling code devices (which generate a new code on each press) became available.
Rolling code technology ensures that each signal transmitted by the remote control is unique and cannot be reused for unauthorized access.[5] This innovation, widely adopted in remote car keys and home security systems, significantly increased the security of garage door operators by preventing signal capture and playback attacks.
Third Stage: of the garage door opener market uses a frequency spectrum range between 300-400 MHz and most of the transmitters/receivers are based on jumping or rolling code technology. This approach prevents criminals from recording a code and playing it again to open a garage door. Since the signal is supposed to be significantly different from that of any other garage door remote, manufacturers claim that it is impossible for anyone other than the owner of the remote to open the garage. 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 accept in the future. Because there is a high probability that someone will accidentally press the unlock button while out of range and desynchronize the code, the receiver generates look-a-head codes in advance. Rolling code is the same security method used in remote car keys, and in some Internet protocols for secure sites.
Fourth Stage: This stage of garage door openers is similar to the third stage, but is limited to the 315 MHz frequency. The 315 MHz frequency range prevents interference from the Land Mobile Radio System (LMRS) used by the US military.
The following standards are used by units manufactured by Chamberlain (including LiftMaster and Craftsman).
* Not applicable to numeric input keyboards or universal controls.[6].
Units manufactured by Overhead Door Corporation and its subsidiary The Genie Company use the following standards:.