<P> By itself, frequency hopping provides only limited protection against eavesdropping and jamming . Most modern military frequency hopping radios also employ separate encryption devices such as the KY - 57 Speech Security Equipment . U.S. military radios that use frequency hopping include the JTIDS / MIDS family, the HAVE QUICK Aeronautical Mobile (OR) communications system, and the SINCGARS Combat Net Radio, Link - 16 . </P> <P> In the US, since the Federal Communications Commission (FCC) amended rules to allow frequency hopping spread spectrum systems in the unregulated 2.4 GHz band, many consumer devices in that band have employed various spread - spectrum modes . </P> <P> Some walkie - talkies that employ frequency - hopping spread spectrum technology have been developed for unlicensed use on the 900 MHz band . Several such radios were marketed under the name eXtreme Radio Service (eXRS). Despite the name's similarity to the FRS allocation, the system is a proprietary design, rather than an official FCC allocated service . </P> <P> Frequency - hopping spread spectrum technology is also used in some RC (radio controlled) car transmitters and receivers . </P>

Difference between frequency hopping and direct sequence spread spectrum