Abstract: A programmable apparatus is disclosed for generating a frequency modulated signal at a selected center frequency in accordance with digital data of at least first and second data levels. The modulating apparatus comprises a modulator having an input and an output and is responsive to an input modulation signal applied to its input for generating at its output the frequency modulated signal at a center frequency dependent on a quiescent voltage appearing at its input. A circuit is provided for sampling and storing a value of the quiescent voltage. An addressable memory stores a plurality of offsets. A programmable adding circuit adds a downloaded offset voltage to the stored value of the quiescent voltage to output a high modulation voltage. A programmable subtracting circuit subtracts a downloaded offset voltage from the stored value of the quiescent voltage to provide a low modulation voltage.

Abstract: A programmable apparatus is disclosed for generating a frequency modulated signal all a selected center frequency in accordance with digital data of at least first and second data levels. The modulating apparatus comprises a modulator having an input and an output and is responsive to an input modulation signal applied to its input for generating at its output the frequency modulated signal at a center frequency dependent on a quiescent voltage appearing at its input. A circuit is provided for sampling and storing a value of the quiescent voltage, An addressable memory stores a plurality of offsets. A programmable adding circuit adds a downloaded offset voltage to the stored value of the quiescent voltage to output a high modulation voltage. A programmable subtracting circuit subtracts a downloaded offset voltage from the stored value of the quiescent voltage to provide a low modulation voltage.

Abstract: An interface device interacts between a digital data terminal and a frequency modulated analog transceiver module to control data flow between the digital data terminal and the transceiver module and to adapt the transceiver module to transmit digital data signals and to communicate messages containing digital signals to the digital data terminal. The interface circuit includes a digitally implemented signal shaping circuit which samples an analog quiescent state bias signal level of a voltage controlled oscillator circuit of the transceiver module. The signal shaping circuit samples and converts the sampled quiescent bias signal level to an equivalent digital data value. The digital equivalent value is increased by and decreased by a predetermined deviation value, thereby generating equivalent values of high and low modulation bias voltage levels.