On the earliest garage door openers, the door could only be opened by a keypad mounted outside the garage door and hardwired in or a push button inside the garage. As technology improved the remote was invented and originally one remote would open your garage door, but it would also up any other garage door it was in range of.
Next came the invention of the DIP pin system (Also called DIP switch) were each opener and remote had 12 DIP pins. The DIP pins on the opener unit would be set identical to the DIP pins on the remote. This allowed each opener to have its own preset code.
Then came the changing DIP pins that would allow the owner to program one or more remotes to their opener. This was accomplished by sliding each of the nine DIP pins into matching position on the opener and the remotes. These DIP pin settings would set the frequency the opener and remote operated on. These DIP pins frequencies operated in the 300-400 MHZ range. This system worked fine until security became an issue because remotes were developed to quickly run through all frequencies in the 300-400 MHZ range thus finding the correct frequency to open a given garage door. Criminals also found they could make code grabbers that could record and retransmit a signal to open a garage door.
The next stage of remotes operated in the 390 MHZ frequency, but new technology provided for rolling codes. This system automatically recoded both the transmitter(remote) and the receiver(opener) to a new but common code each time the remote was used to open or close the garage door. This system made it virtually impossible for a criminal to record and duplicate the code used to open and close the garage door.
The next stage still used rolling codes, but switched to the 315MHZ to get away from the Land Mobile Radio System (LMRS) used by the U.S. Military. This change helped decrease interference since most things operate on 390 MHZ. Most modern remotes operate on a rolling code type system and dependant on the brand operate on 310, 315 and 390 MHZ.
