Rolling code
A remote-control security system that changes the transmitted code after every use so a captured signal cannot be replayed.
- Fixed code — note the DIP switch bank inside older remotes
- Rolling code, on every current opener
Early garage door remotes sent one fixed code, which could be captured and replayed by anyone with a scanner, or matched by a code grabber cycling through combinations. Rolling code — also sold under manufacturer names such as Security+ — changes the code every time the button is pressed.
All current openers use rolling code. If an opener is old enough to use a fixed code and a bank of DIP switches inside the remote, that is a security reason to replace it in its own right.
Rolling code is also why a remote sometimes needs re-pairing after a battery change or a power cut: the receiver and transmitter have to resynchronise.
There is a practical test for whether an opener is old enough to be a security concern. Open the remote: if it contains a row of tiny sliding switches rather than just a battery and a board, it is a fixed-code unit from before rolling code became standard, and its code can be captured and replayed. That is a reason to replace the opener on its own merits, whether or not it still works. On a current unit, occasional re-pairing after a battery change or a power cut is normal rather than a fault, because the transmitter and receiver have simply fallen out of sync.
Remotes in the United States typically transmit around 315 or 390 MHz, and that band is crowded. The most common modern complaint is range that collapses for no apparent reason after a bulb change: many LED and CFL lamps emit radio noise across exactly those frequencies, and one fitted inside the opener housing can cut a remote's working range to a few feet. If your range dropped suddenly, swap the bulb for an incandescent or an opener-rated LED before assuming the remote or the receiver has failed. It is the cheapest test available and it resolves a surprising share of cases. Metal shelving, a new Wi-Fi access point or a neighbour's opener on the same frequency can all produce the same symptom, so change one thing at a time.