22-06-2013, 11:37 AM
DIGITAL BASICS
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Introduction
Digital techniques are now well established in the world of broadcasting. This is due to the fact that though the digital system seems more complex, however, it has many advantages, such as higher accuracy, stability, flexibility etc. Therefore, in spite of their complexity and higher costs, digital circuits are being used for great variety of operations. Secondly with the easy availability of digital circuits in I.C. forms, extreme large digital circuits can be reliably built in small volumes at relatively low cost.
In broadcasting, digital techniques are being used in tape recorders, mixers, switchers, signal processors, level control, reverberation generators, remote control of air-conditioning plants, automation in recording, studio-transmitter links, control and tuning of transmitter etc.
Analogue and Digital Signals
A continuous signal is known as analogue signal. It has many continuous values. On the other hand, a digital signal has discrete values – either it is available or not available. The input to and output from a microphone, the output of a loudspeaker, a singer singing a song etc. are examples of continuous signals. A switch is being switched ON and OFF; the output available is a digital signal.
Logic Gates
Logic gate is somewhat similar to normal gate. When a gate is opened something is allowed to pass and when it is closed nothing is allowed to pass through. But logical gate things logically and then acts. It works with certain conditions. When all the conditions are fulfilled input is allowed to pass as output.
A logic gate is a digital circuit with one or more inputs, but only one output. The output is high only for certain combinations of the input signals.
We have different types of gates such as AND gate, OR gate, NOT gate etc. These can be designed with the help of switches, diodes, transistors and ICs. Let us discuss these gates one by one.