The TH72035 FSK/ASK transmitter IC is designed for applications in the European 868 MHz industrialscientific-medical (ISM) band, according to the EN 300 220 telecommunications standard. It can also be used for any other system with carrier frequencies ranging from 850 MHz to 930 MHz (e.g. for applications in the US 902 to 928 MHz ISM band). The transmitter's carrier frequency fc is determined by the frequency of the reference crystal fref. The integrated PLL synthesizer ensures that each RF value, ranging from 850 MHz to 930 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.