Analog to digital conversion

The basis of high fidelity telecommunication is the binary signal created by a process called analog to digital conversion. The binary signal is a reliable carrier because it consist of only two possible values, making it much less susceptible to the effects of noise and distortion. Analog  to digital conversion begins with sampling, it consist measuring the amplitude of the analogue waveform at equally spaced intervals of time. The difference between  the highest  and lowest frequency of the waves making up the signal is known as bandwidth. In order for the sampled signal to be then stored or transmitted in digital form, each sampled amplitude must be quantized, converted to one of finite number of possible values or levels. For ease in conversion to binary form, the number of levels is usually power of 2 ,and so on depending on degree of precision required. The degree of inaccuracy depends on the number of output levels used by the quantizer. More quantization levels  increase the accuracy of the representation but they also increase the storage capacity or transmission speed required.in the next step in the digitization process the output of the quantizer is encoded into a binary sequence. The three bit code shown in the can represent eight levels .16 levels would require four bits and 256 levels would require eight bits. When a digital signal hasa to be changed back to an analogue one, the decoding produces a stepped waveform if a high sampling frequency has been used the steps are very small  and the decoded signal is a good copy of the original analogue signal