By the 1970s the technology had slightly advanced and there were new models on the market; however these were not a flawless design and were built using a DIP switch.
The DIP switch contains eight smaller switches which were used to contain a code. This code would be sent from the transmitter to the receiver which would be located in the car or garage. The device would only work if the receivers DIP switch was set with the same code. The one problem with these remote entry devices was that eight DIP switches could only create two hundred and fifty six different code combinations; this then caused more security problems.
Today technology is expanding at a fast pace and remote entry devices are very focused on making sure that your garage or car is secure and safe. With the increase of radio scanners picking up your codes, the current remote entry devices are programmed to change the codes each time you use them. This is called a rolling code or hopping code system. This system is much more secure, and the transmitter and receiver are designed to work on the same code basis. Once you use the remote entry device, the transmitter and receiver generates the next code they will use and stores it in their memory.
This code is selected by the pseudo random number generator that is used by both the transmitter and receiver. The receiver will only perform the required function if it receives the correct 40 bit code; however it is also designed to except the two hundred and fifty six rolling codes that follow after that, so when you have put your keys in your pocket or bag and the remote entry device is attached to them, if the button gets pressed your remote entry device will still work. If the button on the remote entry device is pressed more than two hundred and fifty six times, it will not work any more and will need to be reset.
When the generated 40 bit code is sent by the transmitter, a function code is also sent to the receiver so that it can detect the required task. For example open door, set alarm, close door etc.