The keychain remote is block coded, which means you can use this on the Linear AE100, AE500, or AE1000 systems that are programmed via modem or PC connection. The transmitter is MegaCode format, which means each transmitter is factory preprogrammed with one of over 1,000,000 codes, virtually eliminating the possibility of code duplication. Because the receiver ”learns” each specific code, no unauthorized person can gain access to the system by reprogramming a transmitter.