If you are looking for the first time to this topic, you probably never realized how many different types of RF encoding technologies exist. They are mainly 3 types of techniques developed in the past decades:
- Fixed Code
- Computer/Learning/Million Code
- Rolling Code
Each technique have been used by different manufacturers with different encoding implementations.
Fixed code remote transmit exactly the same code every time button is pressed, which means if somebody is using a radio signal interceptor when you’re pressing the button, he can record the signal and repeat when you’re not around home, and open your garage or gate. Some other simpler techniques can be used, as testing each code combination one by one with an original remote, or even with an automated transmitter. In older 12bits remotes this would mean 4096 combinations. Not so hard to found the right combination after some minutes or hours.
Computer/Learning/Million Code transmitter appear to overcome this problem, using a higher bit count (18, 24, 28bit) and million combinations. However this is still a fixed code remote, and likely to be copied with a radio signal interceptor.
So Rolling Code comes to change this situation, since the rolling code part is encrypted everytime, the transmitted signal is always different, so even if someone recorded one transmission, the receiver would discard the signal if the same code has been transmitted twice.
Other reason why Rolling Code is so popular, is that it has some technical barrier, making manufacturing compatible remotes even more difficult, so original brand makers can keep much higher profit selling these original remotes. This is a obvious marketing advantage why more and more manufacturers are using rolling code remotes.
Nowadays among the major brand names, only Came Top432na still uses fixed code technology, however there are lot of products in the market and lot of equipment’s still working with fixed code technology by using PT2262/PT2240/eV1527 chips. They work very well in most circumstances and are expected to continue in the market for many years.
Here at LMPAutomation we have studied the original remotes in order to found how exactly they implemented these existing technologies. In the following blogs you will be able to found the progresses we made during this path.
HCS301 Rolling Code single transmitting sample: