Pulse Code Modulation

Data can be represented either in analog or in digital form. An analog signal can have infinitely many levels of intensity. Example: when a person speaks than an analog wave is created in the air. The signal is represented in the form of vertical and horizontal lines. Signal is represented in the form of curve. The curve representing the analog form is simply like passing through an infinite number of points. The horizontal line represents the time and, vertical signal represents the value or strength of signal. Analog signal can be "periodic" or "a periodic".

Here in this you will know about: how PCM is used to convert the analog signals to digital signals?

PCM include following four processes which will be used to convert the analog signals into digital signals:

· Sampling

· Quantization

· Binary encoding

· Line encoding

SAMPLING IN PAM

To send or to store into memory analog signals have to be converted into digital signals like song i.e. your analog data when stored into memory. First, it will be converted into digital signals. To convert the analog signal into digital signals first, the analog signal will be converted into "bars" when analog signal will under go sampling. This process of sampling is known as "PAM" (pulse amplitude modulation).

PAM is not useful for data communication because even though it translates the original waveform to a series of pulses, these pulses are still of any amplitude. To make them digital, we must modify them by using pulse code modulation.

QUANTIZATION

"PCM" modifies the pulses created by "PCM" Pulse Amplitude Modulation to transform the ampltiude into digital signals. PCM is the sampling method used to convert PAM pulses. For this purpose, we do quantization on the analog signal after sampling. Quantization is a method in which values are assigned to sampled instances.

BINARY ENCODING

After quantization the amplitude values will get converted to bits. The number of bits is 8 to represent the amplitude value. Out of these 8 bits 7 bits are used to represent the amplitude value and the rest 1 bit i.e. the first bit is used to distinguish between the signal's amplitude sign. If this sign is positive than the bit will be 0 else it will be 1(i.e. for negative amplitude value). This technique of converting the amplitude value to the binary digits is known as BINARY ENCODING.

LINE ENCODING

PCM is actually made up of 4 processes: PAM, QUANTIZATION, BINARY ENCODING, LINE CODING. Now, as the analog signals are converted into binary encoding, the problem lies how to send these signals? The binary representation of analog signals will undergo through "LINE ENCODING". And the signals will be transmitted bit by bit by using this line encoding method.