As the ceaseless development of information network, the digitlization monitoring technology that is a foundation with multimedia and network has arrived deep in the job of people, study and life. Monitoring technology forward network, digitlization develops ceaselessly, and the wide application that a of monitoring information main feature is multimedia technology. Multimedia includes character, sound, image, graph to wait, have information content capability of big, expression is strong wait for a characteristic, accordingly it replaces onefold information mode to had become the tide that cannot resist. Regard multimedia as the most important part in information, the video information that digital video place provides has intuitionistic sex, exact sex, efficient sex, extensive sex to wait a series of advantage, but video information has information content to pass big question. The efficiency that because this must solve video,reduces and video reduce the quality problem of decipher.
In video supervisory system, coder basically inspects imitate frequency signal compresses data encode file, decoder is communication decoder and dc decoder according to cent of voltage of cloud stage power supply. Communication decoder communicates 230V to communicate cloud stage to offer or stage of cloud of 24V voltage drive turns; Dc cloud stage provides dc 12V or 24V power source for dc cloud stage, if cloud stage is gearshift pilot asks dc decoder is the cloud even,the stage provides 0-33 or signal of 36V volts d.c. , the gearshift that will control dc cloud station is rotational.
According to communication means cent is one-way communication decoder and two-way communication decoder. The voltage that one-way communication decoder receives the communication signal that comes from controller to be its interpreter corresponding movement only / equipment of front of voltaic signal drive; The decoder of two-way communication still sends communication signal to controller besides the property that has one-way communication decoder, because this is OK,real time conveys the working status of decoder to undertake an analysis to controller, can measure newspaper police officer additionally implement the newspaper police officer that spot of be widely read comes to by two-way communication in waiting for front equipment signal to input decoder directly measures signal, reduce the use of wire cable.
Can divide according to the transmission means of communication signal be transmitted for coaxial and double skeining thread is transmitted. General decoder supports the communication signal that double skeining thread transmits, and some decoder still support or at the same time supportive coaxial cable transmits means, pass communication signal modulation and video signal to be transmitted jointly with different frequency namely in same on video cable.
The circuit of decoder is with sheet piece machine for core, reach address input, output by power source circuit, communication interface circuit, self check drive circuit, call the police the circuit composition such as input interface. Normally, decoder cannot be used alone, and need and systematic lead plane cooperate to use. We will be everybody's farther introduction below product of a few decoder.