When considering a radio for the system, legal considerations are just as important as technical considerations. Various governments regulate the radio spectrum within their countries and specify what can and cannot be done at a particular frequency. Understanding the legal requirements in the countries in which the end product will be sold is the first place to start when choosing a radio. Fortunately, many governments have recognized the advantages of globally consistent regulations, so the requirements for remote control systems tend to fall into two camps. The United States Federal Communications Commission (FCC) has specified the 260MHz to 470MHz band to be used for the transmission of command and control data. There are a number of requirements and restrictions in this band that are intended to keep it clear of interference. Linx Application Note AN-00125 goes into the regulations in this band in detail. Canada and Brazil have adopted regulations that are very close to the US regulations, with the 315MHz and 433.92MHz being the most common frequencies for RKE in these countries. The European Union has adopted a different set of regulations, but these regulations are followed by all member countries as well as several Pacific and Asian countries. Europe has allocated the 433.05MHz to 434.79MHz band for remote control and command applications. Since this band is so narrow, the center of the band (433.92MHz) is typically chosen so that products still fall within the band over temperature and component variations. This frequency overlaps the FCC band, meaning a single 433.92MHz radio design can be used in the U.S., Europe and many other countries. This makes hardware design and manufacturing efficient, but it also makes the band crowded with devices. It is up to the designer to understand the regulations and determine the best frequency of operation for the product.