Monday, November 19, 2012

Physical Layer

Physical Layer Basics
Physical layer is the basis of all the networks in the OSI reference model that is characteristic of hardware whose function is to transmit data signals both analog data and digital data. Besides the physical layer of the system is also a means to send data to other devices connected within a computer network.
The physical layer is the lowest layer of the OSI reference model that serves to determine the characteristics of the cable used to connect computers in a network. On the transmitter side, the physical layer functions apply electrical, mechanical, and procedures to establish, maintain and release the communication circuit to transmit information in the form of digits Binner to the side of the receiver. While the physical layer on the side of the receiver will receive and transmit the data to the upper layer.
Signal Data
In the communication process, the data will be transmitted first encoded in the form of analog signals and digital signals.
1.      Analog Signals
The analog signal is a signal waveform data in the dial-connect or continuous, there is no sudden change and have the scale, the amplitude and frequency.
By using analog signals, then the data transmission range can reach distances, but it is easily affected signal noise. Waves in general sinusoidal analog signal that has three basic variables, namely amplitude, frequency and phase.
a.      Amplitude
Amplitude is a measure of the high and low voltage analog signals. The images below will show more clearly what is meant by amplitude.
b.      Frequency
Frequency is the number of analog signal waveform in one second. The interface can be seen in the picture below.
c.       Phase
               Phase is a great angle of the analog signal at a given time. Phase at angles 00, 900,  1800, 2700, and 3600. 
  Digital Signal
A digital signal is a signal in the form of pulses of data that can undergo sudden changes which have scale 0 and 1 as shown in the picture below.
A digital signal has only two states, that is 0 and 1, which are not easily affected by noise, but the transmission of digital signals only reach the range of data dispatch close relative.
In the process of data transmission, disunakan a tool called a modem. Modulator standard modem demodulator. As a modulator, the modem will translate the data or information in the form of a digital signal into an analog signal which then combine with the carrier frequency (carrier), while the demodulator, the modem will separate from the carrier frequency and translates the data or information signals are analog signals into digital form.
There are four possible pair of data signal shape and signal transmission that occurs after experiencing a data transmission process. 

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