Design And Research Of Transmitting And Receiving System Of Multimedia Phone

For the sole communication mode of fixed telephone,we make innovation to the ordinary fixed telephone terminal to develop the multimedia phone which adds LCD display module, graph and text transfering module based on fixed telephone. It is the DSP (Digital Signal Processor) which processes the graph-text information and audio signal and control the display module and input module. At the same time the audio signal and graphics signal are transfered in the ordinary analog telephone lines by frequency-division multiplexing. The graph-text signal that was transfered in the telephone line and don't affect the quality of audio signal will enhance the comprehension between the speaker and the audience.The new communications equipment can effectively cleared the misunderstanding caused by the dialect,can meet the visual display requirement of graph, line, other design in the remote teaching which would effectively improve the teaching quality, facilitate the communication for the deaf and dumb, greatly reducing the restrictions on the users,and in some special cases,have a secret communication.In the sending terminal,when the phone was through, the speaker write or draw in the handwriting board which get the graph-text signal and input the signal into the DSP for processing. The signal is sent to the LCD module to display,at the same time the graph-text signal are modulated by the DSP for transfering in the phone line.And the modulated graph-text signals were converted into analog signal by the IC of TLV320AIC23B. Finally, the analog graph-text signals was send to the fixed telephone network with lowpass filtered audio signal.In the receiving termianl,telephone received the mixed-signal of audio and graph-text from the fixed telephone network which was transmitted from the transmitter. Then the mixed-signal was passed to low pass and high pass filter circuit to be decomposed into separate audio and graph-text signals. The former was send to the telephone and was converted to sound. An analog-digital conversion module converts graph-text signals into digital signals in the DSP. After demodulation, finally, the digital graph-text signals were transferred to the LCD display.