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The encoders and decoders can come in a variety of flavors and there are several considerations in choosing the best technology for an application. First, some different levels of technology are presented. Low security systems have addresses that are set by DIP switches or cut traces. As long as the address is set the same on both ends, a transmission is accepted. These systems were used in the first garage door remotes. They are simple to implement but have a limited number of addresses. Since every address line needs its own switch or trace, the hardware implementation gets cumbersome over about 10 lines. This limits the system to around 1,024 unique addresses. These systems are not very unique, so there is a greater chance of another system in proximity having the same address and unintentionally activating the system, meaning someone in a neighborhood could end up turning on the wrong sprinkler system. These systems are not secure, but the simplicity is an advantage in some applications. Medium security systems have a large number of address bits to significantly increase the uniqueness. These systems set the address either through a programming interface or by a randomization routine based on a button press. They typically use either 24 or 32 bit addresses, giving 16.7 million to 4.3 billion unique addresses. This greatly reduces the chances of unintentional activations. This address is then learned by the decoder to give the encoder authority to activate the system. There is no encryption so they are not secure. These systems are a bit more complicated to set up, but they benefit from the greater number of addresses and possibly lower hardware costs.
