Introduction - If you have any usage issues, please Google them yourself
In this system, the message sequence prior through FSK modulation, through the cut-off frequency of 25kHz after low-pass filter (to limit the frequency 25kHz), and then move into the mixer to a higher frequency to send out, at the receiving end used with frequency hopping synchronization signal transmitter carried on their conversion (FH' s solution to deal with this for jumping), take down side frequencies, then the demodulation of FSK