Garage doors are typically opened remotely using a handheld device known as a clicker. When activated, the clicker sends a signal to the receiver installed in the opener of your garage door. Clickers for garage doors were one of the first devices used for remote entry control and were developed in the 1950s. Because all of them operated on a single frequency, they lacked in security. Security features were added about twenty years later through so called DIP switches. These switches installed both in the clickers and receivers made the frequencies more unique. A DIP switch setting acted like a password shared between the signal sender and receiver and could be changed manually. The door opened only for a matching setting. However, due to the relatively small number of possible combinations, this solution was not very secure either. Furthermore, the transmitted signal could be recorded and sent again by someone wishing to break into your garage. This problem was addressed by newer technology. The clicker and receiver today contain a chip which generate "rolling codes" - on each use, an identical, unique code to be used for the next door opening operation is generated in both devices. Over time, other devices, such as electronic keys for car doors, were developed that operate using similar principles.
