Time multichannel communication introduces

From;    Author:Stand originally

PCM transmits a system

Signal of imitate of one's voice in speech is in send upright course to sample, quantify and PCM got after encode (pulse encode modulation) signal, this signal sends pair of end through transmission line. The PCM stack that will get in sink is reductive into signal of imitate one's voice in speech.

Time multichannel answer with

To raise line utilization rate, always try to be in pile transmission line to go up, transmit the information of many telephone channel, this is multichannel answer with.

Multichannel answer is used normally frequency cent is made, time is made and pile up cent to make 3 kinds.

Frequency cent is made is to will transmit frequency band to be divided into N part, the transmission channel that each part all can become independent as is used. If plan institute is shown. There can be information of N dialog road to convey on a pair of transmission line so, and what place of each dialog road takes up is an among them frequency only paragraph. Frequency cent makes communication call carrier wave communication again, it is the main measure that imitate corresponds.

Time is made is have a transmission channel time is broken up in order to convey the information of a certain number of telephone channel, if plan institute is shown. N telephone channel equipment receives passageway of a common to go up, allot the time of a paragraph of use passageway to each equipment by certain order alternate. When be turn for a certain equipment, this equipment and passageway put through, executive operation. Meanwhile, the connection of other equipment and passageway all is cut off. Wait for designation use time-interval to arrive, receive passageway couplet through time multiplexer the next should go on connective equipment. Time makes communication also say time breaks up communication, it is the main method that digital phone multichannel corresponds, consequently PCM communication often calls time multichannel communication.

The fundamental of PCM

Make in time in, each user (in be like a graph all the way, the 2nd, ... ) in appoint communication is received to inside time, other time is pressed for other user when appointing, connect secondhand, to make inchoative each are mixed receive end each can mutual correspondence is harmonious work consistently, in inchoative need to convey a synchronous signal, use synchro control signal to ensure inchoative and receive end to coordinate the work. In time multichannel communication, how does total time decide? How much route can be you arranged inside this total time?

In the course that is changed into digital signal from signal of imitate of one's voice in speech knowable, to ensure sink can the digital signal disperse is reductive into successive imitate signal, sampling frequency needs to use 8000 hertz, namely every other sampling of 125 small seconds, accordingly, the time communication with respect to PCM, be divide time of 125 small seconds into a lot of small stage, every take period of time all the way, this time calls time slot. Apparent, a movement in martial arts is more, every time slot is smaller. Normally arrangement has 24 road, 32 wait, our country uses the PCM30/32 that CCITT suggests to make type make the primary group of multiplexing for the time of standardization.
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