Remote Control
The first wireless garage door openers were invented and developed by two US inventors at the same time, one in Illinois and the other in Washington state. They were unknown to each other.
The first garage door opener remote controls were simple and consisted of a very simple transmitter (the remote) and receiver which controlled the opener mechanism. The transmitter would transmit on a designated frequency; the receiver would listen for the radio signal, 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. While novel at the time, the technology ran its course when garage door openers became 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 is 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 dealt with the shared frequency problem. To rectify this, multicode systems were developed. These systems required a garage door owner to preset a digital code by switching eight to twelve DIP switches on the receiver and transmitter. While these switches provided garage door systems with 28 = 256 to 212 = 4,096 different codes they were not designed with high security in mind; the main intent 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 re-transmit a signal, or code scanners, that would attempt every possible combination in a short time. Multicode openers became unpopular in areas where security was an issue, but due to their ease of programming, such openers are often used to operate such things as the gates in gated apartment complexes.
The third stage of garage door opener market uses a frequency spectrum range between 100-400 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. Since the signal is supposed to be significantly different from 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 receiver generates look-a-head codes ahead of time. Rolling code is the same method of security used on the clickers of cars, and with some internet protocols for secure sites.
The fourth stage of garage door opener systems is similar to third stage, but it is limited to the 315 MHz frequency. The 315 MHz frequency range avoids interference from the Land Mobile Radio System (LMRS) used by the U.S. military.
| Dates | System | Color of programming button (on Chamberlain manufactured units) |
|---|---|---|
| 1984–2004 | 8-12 Dip Switch on 300-400 MHz | white, gray, or yellow button with red LED |
| 1993–1997 | Billion Code on 390 MHz | green button and green or red LED |
| 1997–present | Security+ (rolling code) on 390 MHz | orange or red button with amber LED. |
| 2005–present | Security+ (rolling code) on 315 MHz | purple button with amber LED |
| 2011–present | Security+ 2.0 (rolling code) on 310, 315, and 390 MHz | yellow button with amber LED and yellow antenna wires |
Read more about this topic: Garage Door Opener
Famous quotes containing the words remote and/or control:
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—Friedrich Nietzsche (1844–1900)
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—Alicia F. Lieberman (20th century)