Quiz 9: Data Transmission
In data communication the information is stream of bits obtained by converting analog signal to digital format by means of PCM or other modulation technique. Here the data stream resembles the information of analog signal voltage. But to encode some special characteristics such as symbols or alphanumerical we have separate data code and is known as character code. The character code is of three types. • Data link control character • Graphic control character • Alphanumeric character Data link control character provides flow of data such that it reduces the data error during transmission and flow control. The graphic control character data is useful to align or presentation of data at the receiver. Similarly alphanumeric characteristics are used to encode special symbols or numerals into its predefined bit stream.
Binary data is the non-character data, that is, is usually represented with help of ones and zeros. Examples of binary data are digitized audio and video signals. The principal says that, binary data does not require character code. Now the systems which are primarily designed for transmission of characters can cause confusion, when binary data is used for transmission purpose because these systems has divided all the data into blocks, which have usually seven to eight bits. 'Characters' is the term referred to these small data blocks. Now these systems have used some characters which are defined as control characters. These control characters has some of the important functions, such as, it helps in changing the way system can operate and it can also disconnect the communication link. So, when binary data is used for transmission purpose using these systems, then special care must be taken as control character must not accidentally formed using binary data. Therefore, this confusion (forming control characters using binary data) should be avoided, so that the respective system can work appropriately.
Baudot code is used to convert alphanumeric and other characters into electrical signals like pulses. It is a five bit code such that thirty two different figures or letters can be translated into electrical pulses. The coding is shown in Table 9.1 in the text book. From the Table 9.1 in the text book the Baudot code can handle thirty two different characteristics such that it can shift either from Figures(FIGS) to letters (LTRS) or vice versa. In either of the cases it can handle either capital letters (UPPER CASE) or simply some special Figures only as shown in the Table. There is no provision or any shift keying to operate for lower case letters. Therefore, Baudot code can handle special figures and upper case letters and it cannot handle or encode lower case letters.
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