Multi Frequency Rolling Code Remote Control
Multi Frequency Rolling Code Remote Control
Rolling code is a security technology that provides a fresh code for each authentication. This makes it harder for criminals to gain access to your home.
Our Solidremote Universal RF Remote Control Duplicator can clone most fixed-code RF remote controls, while it is not possible to clone rolling-code models. Please check prerequisites & cloning tips at the bottom of this page before you start.
Security
A multi frequency remote rolling code control can be a great addition to your home security system. It is also a handy tool to have around the house, especially when you need to open or close your garage door quickly.
Many modern garage door openers use a rolling code system to protect your home from hackers. These rolling code systems generate a new code for every authentication, preventing replay attacks in which an eavesdropper can access a stored code and then re-transmit it to hack the system.
However, thieves have found ways to defeat even the most sophisticated of these security features. Burglars have been able to scan the frequencies used by these remotes with a device called a “code grabber.” These devices can read the codes that you have sent out and then re-transmit them to unlock your garage door, giving the criminal access to your home.
Another way that criminals have been able to break into rolling code systems is by hiding a device near the remote control and waiting for the right moment to press it. Once the remote is pressed, this device intercepts the code and stores it for later use.
If you have a rolling code remote, check it to see if there are any dip switches in the circuit board or on the back of the device. If there are no dip switches, then the remote does not use rolling code technology.
There are also some other signs that a rolling code remote has been hacked, such as if there is no light for the buttons on the device or if there are two separate button sections instead of one. If you notice these, it may be a good idea to buy a new remote.
Rolling codes are a common security feature found on many different types of remotes and receivers. These devices use a pseudo-random number generator (PRNG) that maintains information about the last code that was sent and performs a calculation to determine the next number in the rolling code sequence.
Transmitter
A multi frequency rolling code remote control transmitter generally comprises a fixed code and a variable code that is changed with each actuation of the transmitter.
A receiver demodulates the encrypted RF transmission and recovers the fixed code and the rolling code. The fixed and rolling codes are compared to stored codes and if they match, a signal is generated which actuates an electric motor that opens or closes a movable barrier.
Alternatively, a receiver demodulates the encrypted RF transmission but only recovers the fixed code. The fixed and rolling codes are matched to stored codes in a window forward system in which each incoming code is compared to the next valid code within a set of two consecutive valid codes.
If there is no match, a test is performed in step 766 to determine whether the program mode has been set and if not, the program indicator is switched off. In the event that it is set, there is a return from the interrupt sequence and control is transferred to a step 772.
Another advantage of a multi frequency rolling code remote control is that it can be used with most brands of garage door and gate operators. The transmitter can store 4 different frequencies of fixed and rolling code, allowing you to create and use an unlimited number of remotes with one single device.
The transmitter also offers a window forward security system wherein each incoming code is compared to the previous code within a set of two consecutive valid code windows. The first window provides a valid code, the second relatively insecure code window requires two successive valid codes to be received and finally the last relatively insecure code window does not recognize any codes because it is likely that the receiver has been stolen.
To achieve this, the alternating trinary bits comprising the fixed code and the rolling code are shuffled so that they form a plurality of digits of an odd number. The resulting number of digits is then assembled into two frames, each frame comprising 20 trinary bits with the first frame identified by a 0.5 millisecond sync bit and the second frame being identified by a 1.5 millisecond sync bit.
Receiver
Many multi frequency rolling code remote controls include a receiver or radio receiver 12 that is configured to receive the rolling code signal transmitted by transmitter 10. The receiver 12 can be an electronic device containing one or more microprocessors, microcontrollers, application-specific integrated circuits, volatile and/or non-volatile memories, and radio frequency transmit and/or receive components such as transistors, inductors, antennas, etc.
Transmitter 10 and receiver 12 each include a user input device 16, 18 for transmitting and receiving radio frequency messages or signals to activate remote system 14. This can be a push button, switch, dial, touch-screen display, voice or speech-recognition system, or any other type of user interface.
During a training operation, at least two rolling code signals or messages with different sequential counter values are sent by trainable transmitter 30 in response to a user input device 34 (FIG. 1). Each message includes an encrypted counter value and a transmitter identifier. The first message is synchronized with the receiver, and the second message is used to activate a garage door opener.
For example, if the first and second messages are sent for a garage door opener, then when a garage door is opened, a counter value 26 associated with transmitter ID 20 is incremented, and IncRoll is decremented by one. Then, if the variable IncRoll is not equal to zero, a second rolling code message is sent with a different sequence of encrypted counter values. The two message synchronizations and counter incrementing can be controlled by the duty cycle of a radio signal transmission, or can be delayed in time to comply with Federal Communications Commission regulations.
The trainable transmitter 30 can be a new remote control or an existing remote control that is programmed to work with the receiver 12. To synchronize and program the trainable transmitter 30 with receiver 12, the user presses the buttons on the trainable transmitter and the original transmitter within a close range of each other (e.g., a few inches).
The original transmitter and the trainable transmitter identify each other by their radio frequency signal received from each other, and the counters of both transmitters are set to begin at the same value. After the trainable transmitter 30 is programmed, a user can then simply press a button on the trainable transmitter a few times to activate the garage door opener. The system will then synchronize and provide visual or audible feedback to the user that it was successful.
