My project is about creating a transmitter using the low frequency range (30kHz -300kHz), I am in need of of the right circuits to put together that would map both the voice and digits to frequency, that is, for every sample inputted into the system through a mic condenser for example, frequency is being generated and for the digits, for every key pressed, the voltage levels are converted to frequency and can be transmitted at low frequency range. I hope the little explanation given gives an idea of what I am trying to talk about and any help what so ever will be really appreciated.