Garage door opener
Most also include a handheld radio remote control carried by the owner, which can be used to open and close the door from a short distance.
[2] As in an elevator, the electric motor does not provide most of the power to move a heavy garage door.
A quick-release mechanism is attached to the trolley to allow the garage door to be disconnected from the opener for manual operation during a power failure or in case of emergency.
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, around 1930.
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.
More sophisticated intruders could acquire a black box master key that automatically transmitted every possible code in a short time.
An intermediate stage of the garage door opener market eliminated the DIP switches and used remotes preprogrammed to one out of roughly 3.5 billion unique codes.
For user convenience, these systems were also backward compatible with the older DIP switch remote codes, but adding an old technology remote to the security list made the garage door opener vulnerable to a brute force attack to find the DIP switch code.
In addition to transmitting a unique identifier for the remote control, a sequence number and an encrypted message are also sent.
The encryption makes it extremely difficult for an intruder to forge a message with the next sequence number that would open the door.
Rolling code technology is also used on car remote controls and with some internet protocols for secure sites.
The 315 MHz frequency range avoids interference from the land mobile radio system (LMRS) used by the U.S. military.
The following standards are used by units manufactured by Chamberlain (including LiftMaster and Craftsman): * Does not apply to keyless entry keypads or universal remotes.
Recent Chamberlain garage door openers that have Security+ 2.0 features also use a special serial protocol on wired connections rather than a simple switch closure.
[5] The following standards are used by units manufactured by Overhead Door Corporation and its subsidiary The Genie Company†: † Note: There are no standard color codes for the learn button or LED on units manufactured by Overhead Door or Genie.
Many garage door opener remote controls use fixed-code encoding which use DIP switches or soldering to do the address pins coding process, and they usually use pt2262/pt2272 or compatible ICs.
[11] A requirement for redundant entrapment-prevention devices was added in 1993; such a system can use an electric eye, a door edge sensor, or any other device that provides equivalent protection by reversing the travel of the closing door if an object is detected in its path.
Jerry Brown on Sept. 21, 2018, in response to the 2017 California Wildfires in which at least 5 individuals lost their lives because they could not open their garage door when the power went out.
