Garage door opener

A garage door opener is a device for remotely opening a garage door.

History

The first garage door opener systems were simple. A system consisted of a simple transmitter (the remote) and receiver (the opener). The transmitter would transmit at designated frequency; the receiver would listen to a change in amplitude, then open or close the garage, depending on the door position. The basic concept of this can be traced back to World War II. This type of system was used to detonate remote bombs. Therefore the original garage door opener was a glorified bomb that could be detonated remotely over and over again. While novel at the time, the technology would run its course when garage door openers would become widely available and used. Then, not only did a person open their garage door, they opened their neighbor’s garage door as well. While the garage door remote used was low in power and in range, it was powerful enough to interfere with other receivers in the area.

The second stage of the wireless garage door opener system was forced onto the market because too many garage door openers operated on the same frequency. To rectify the problem, a more advanced (and more secure) method of opening garage doors was developed. Factories now allowed a garage door owner to preset a “code.” This code consisted of about 8 dip switches on the receiver and transmitter. With these switches the garage door system now had 28 = 256 different “codes.” This new system was not really designed with security in mind. The idea was not to interfere with other garage door openers, and security appeared to be an afterthought.

The current garage door opener market offers a variety of garage door openers. The frequency spectrum ranges between 300-400 MHz. and most of these garage door openers rely on hopping or rolling code technology. Encoders in the transmitter and decoders in the receiver work on a rolling code that prevent perpetrators from recording a code and replaying it to open a garage door. Because the signal is supposed to be significantly different than that of any other garage door remote control, manufacturers claim it is impossible for someone 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 might accidentally push the open button while not in range and desynchronize the code, the transmitter and receiver generate look-a-head codes ahead of time.