Design Of Digital Visiting Phone System Based On Bus

In the prison information management, visiting phone system is used to help the prison managers to understand the mind state of criminals, to mollify their mood and monitor their transformation process. Most of the traditional visiting phone system is the analog style, their anti-jamming ability is weak and the noise is too large and the storage capacity is also weak. The existing digital visiting phone system has the disadvantage that too expensive switching equipment, too complicated wiring, too small capacity and so on. To improve these problems, a visiting phone system based on bus is proposed in this paper, and it is divided into two parts according to different using place, they are digital visiting phone system based on CAN bus and digital visiting phone system based on serial Ethernet.The digital visiting phone system based on CAN bus is mainly used in monitor occasions. The PIC18F66K80 is used as the control core, and its embedded CAN controller and transceiver MCP2551 are used to form CAN bus communication; The codec MC145480 is taken to achieve the coding and reconstruction of the voice;CAN bus is not only used to transmit the voice data but also to transmit control command, and this is the new application mode of the CAN bus.The digital visiting phone system based on serial Ethernet is mainly used in visiting occasions. The controller LPC2132 is used as the control kernel, and its SPI interface and stand alone Ethernet controller ENC28J60 are taken to realize the Ethernet communication; At the meantime using MC145480 for coding and decoding.Ethernet is mainly used to transmit control commands and to upload voice data for the control room monitoring and recording.The digital visiting phone system based on CAN bus has been debugged and put into used. The main function of the digital visiting phone system based on serial Ethernet has been tested completely. The two systems are used in different occasion and have their own advantages. It can meet the requirements of the modern prison.