The Design And Realization Of The Remote Data Acquiring System Based On PSTN

Automation is an eternal theme of mankind's development of science and technology. Mankind is always finding various means and tools to lighten his own working intensity and comfort his own life. Among them, remote data acquiring technology is the most representative. Since this kind of technology appeared , people have paid close attention to it all the time .Among the technology, remote data acquiring technology based on PSTN, with the characteristics of flexibility and practicality^ favoured by many developers and widely used in the fields of Remote-Checking-Meter , TTM and Remote-Monitoring etc.This thesis has put forward a practical scheme for remote data acquiring system based on PSTN. This system is made up of two subsystems,including data acquiring terminal on the spot and central demodulator.The core component of data acquiring terminal on the spot is DSP.DSP can not only complete the task of monitoring and management , but also expand the function of the system in digital filtering and data compressing.The system uses embedded MODEM chip with low price to modulated the data which are transmitted on the PSTN.Central demodulator is based on PCI bus.Despite the outstanding performance, PCI bus is inconvenient to use. The system uses bridge chip to complete the conversion of standard PCI bus to local bus which is convenient to use. The demodulation circuit interfaced with the local bus, demodulates the signals transmitted on the PSTN and restores the acquired data.In order to work nomally, Hardware needs cooperation with software.The driver for PCI demodulator has been developed.The circuit of autodialing has been set up in the data acquiring terminal on the spot. The ring bell detector and the circuit which can simulate picking up the telephone have been set up in the PCI demodulator. Thus, automatic connection from terminal to center has been realized.