[1] Worldwide, a number of similar personal radio services exist; these share the characteristics of low power operation in the UHF (or upper VHF) band using FM, and simplified or no end-user licenses.
Exact frequency allocations differ, so equipment legal to operate in one country may cause unacceptable interference in another.
[1] FRS radios frequently have provisions for using sub-audible tone squelch (CTCSS and DCS) codes, filtering out unwanted chatter from other users on the same frequency.
[2][3] After December 2017, the FCC no longer accepts applications to certify hand-held FRS units providing for transmission in any other radio band.
Under normal conditions, with line of sight blocked by a few buildings or trees, FRS has an actual range of about 0.5 to 1.5 km (0.3 to 1 mile).
The FCC will not certify combination FRS/GMRS radios that exceed the current power limits for the FRS service.
[4] Prior to the 2017 revision, FCC rules required a GMRS license to operate on channels 1–7 using more than 0.5 watts.
As of 2016,[update] only low-power (2 W ERP), half duplex GMRS operation is permitted, but a license is not required.
This allows the use of dual-mode FRS/GMRS walkie-talkies, but precludes the use of higher-powered GMRS devices designed for vehicle and base-station purposes..
However, dual-mode FRS/GMRS equipment is not approved in Mexico, so caution should be exercised in operating hybrid FRS/GMRS devices purchased elsewhere.