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Reviewed January 21, 2015
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Reviewed November 14, 2014
What You'll Get
Choose Between Two Options
- $49 for a multi-point garage-door tune-up and inspection ($100 value)
- $89 for a multi-point garage-door tune-up and inspection plus replacement of up to 12 rollers ($200 value)
Garage-Door Openers: Signaling Security
Learn a little about the technology inside the little remote in your car with Groupon's examination of garage-door openers.
In 2012, garage doors throughout southeastern Connecticut mysteriously seized up. The culprit? A military submarine base.
Annoying as it may have been, there was nothing sinister behind this pattern. Rather, it was simply a side effect of the way all remote-entry garage-door systems are designed. Each time you open or close a garage door, the remote and the receiver inside have a brief conversation in code—a conversation that happens to be conducted via radio signals over the airwaves. The unfortunate homeowners in Connecticut eventually learned that the signal emitted from the submarine base’s radio-communication system shared a frequency with their garage-door systems, and the more powerful military signal drowned out the information their remotes were trying to transmit.
The codes transmitted by garage-door remotes have gotten far more complex over time. As early as the 1960s, burglars learned to use radio scanners or “code grabbers” to pick up the code when the homeowner used it to open the door; they could then re-transmit the code to gain entry themselves. In response, most remotes today use rolling codes that can generate billions of combinations.
This is possible because each time a message is sent between remote and receiver, each part of the system also selects and stores a new code. Those codes will always be in sync because each has been programmed with the same pseudo-random number generator—that is, a formula that produces a sequence of numbers that would appear random to anyone not possessing the formula. (Beware, however: it is possible to desynchronize the system by pressing the remote button out of range of the opener more times than the system’s built-in tolerance for error will permit.) Once this is done, the remote and receiver are ready to kick the system's motor into gear and help you begin or end another day on the road.
The Fine Print
Promotional value expires 120 days after purchase. Amount paid never expires. Limit 3 per person, may buy 3 additional as gifts. Limit 1 per garage door. Valid only for option purchased. Appointment required. Merchant's standard cancellation policy applies (any fees not to exceed Groupon price). Must use promotion value in 1 visit. Residential homes only. Valid only within the following counties: Milwaukee, Waukesha, Racine, Kenosha, Jefferson, and Madison. Roller replacement includes up to 12 rollers, additional fees may apply for each additional roller required. Merchant is solely responsible to purchasers for the care and quality of the advertised goods and services.