The TH72011 FSK transmitter IC is designed for applications in the European 433 MHz industrial-scientificmedical (ISM) band, according to the EN 300 220 telecommunications standard; but it can also be used in other countries with similar standards, e.g. FCC part 15.231. The transmitter's carrier frequency fc is determined by the frequency of the reference crystal fref. The integrated PLL synthesizer ensures that carrier frequencies, ranging from 380 MHz to 450 MHz, can be achieved. This is done by using a crystal with a reference frequency according to: fref = fc/N, where N = 32 is the PLL feedback divider ratio.