Type of Transmission

              Type of information or data signal transmission in a medium can be grouped into two parts, namely the transmission of parallel and serial transmission.
  1.         Parallel Transmission
              In parallel transmission, a connector consisting of seven or eight bits (ASCII) transmitted simultaneously at any time. For example, if use ASCII code, it is necessary to transmit as many as eight lanes as well as 8 bit ASCII code for a single character. Display parallel transmission can be seen in this picture.

              In parallel transmission is transmitted in parallel is the bits that represent a single character, while each character transmitted serially. Parallel communication is used for short distance communication, the transmission of this type normally used to transmit signals inside a computer or between computers to the printer. Examples of this type of communication is a DB-25 parallel.

            Shipping with parallel transmission mode has high speed, because every moment can be directly transmitted one character. However, this transmission mode requires a special cable that consists of several paths to be used in delivery of the bits of the character.

2.         SerialTransmission

Serial transmission is a form of transmission that are commonly used. In serial  transmission, the individual bits of a character are sent sequentially, ie bit by bit, in which one bit followed by the next bit. In this system the receiver will collect the number of bits (for the system ASCII = 8 bits) are sent by the transmitter to then be used as a single character.

Serial transmission can be grouped in three forms, namely Synchronous Transmission, Asynchronous Transmission Transmission and isochronous.

·         Synchronous Transmission

Synchronous Transmission is a form of transmission that transmits serial data or information continuously. Transmission of this type often face the problem, namely the problem of synchronization and bit synchronization character.
The main problem in synchronizing bit is matter of time when the transmitter started putting bits to be transmitted to the transmission medium and when the receiver must know the right time to take the bits that are sent them.

            This problem can be solved with existing clock and clock ditransmitter there direceiver. Clock on the transmitter will tell when to put the bits to be transmitted, for example if you want to send with a capacity of 100 bps, the clock on the transmitter is set to work with a clock speed of 100 bps and the receiver must also be set to pick up from the transmission lines 100 times each second.

            The second problem is the character in Synchronous Transmission synchronization. The problem is in the form of determining a number of bits which are a bits forming a character. This can be overcome by giving SYN character. Generally two or more SYN transmission control is placed in front of the block of data transmitted.
If only used a character kintrol transmission errors can occur false synchronization. To prevent false synchronization, two SYN control characters can be used at the beginning of the block of data being transmitted. Receiver after identifying the form of the first SYN, and then identify the next 8 bits, if it is a SYN control the second character, then after that it starts to count every 8 bits and assemble into a character.

Network Interface Card (NIC)

           Interface Network Card (NIC) or often called a network card (network card), a key component in a network terminal. Its main function is to send and receive the data work sent to the terminal. Besides NIC also control the data flow between computer systems with attached cable system and receive data sent from other computers via cable and translate them into computer-understandable bits.

Although the NIC is produced by several manufacturers, but all can be used to relate to others in a network system commonly used (Netware, Windows NT, and so on).   Compatibility issues are more important is the type of bus workstations, where a network card that is installed. For example, you can not use the network card 32 bit 16 bit bus. But most of the 16-bit network card to work accurately even slower in 32 bit bus. The network card is also designed for a specific bus architectures, many ISA network card into the slot EISA but another type of network card can only go into a particular slot with a particular bus design as well.

Network card or NIC also be purchased as needed, if it is necessary to use UTP cabling network interface card with UTP, as well as when using the BNC cable network card network card is used with BNC interface. But the market is also available network interface card with UTP and BNC once or often called a network card Combo. Network card provides a number of configuration options that ensure the ability of card to be used with other devices in the same computer and give the correct response to the operating system. If you are using a PC-based network, the thing to note is the setting of the NIC to avoid conflicts with other devices.

Why not just use the default settings? in many cases the default settings will provide satisfactory results, because the manufacturer has provided initial setting according to the standard configuration.

Two important variables in the port and the NIC is survived interruptnya.

·         Address port functions to direct dat goes in and out of the terminal work. NIC must be configured to recognize when data is sent to that address.

·         Interrupt a local electronic switch that is used by the operating system to control the flow of data. Interrupt also used mainly by the computer to stop the flow of data for a while waktudan allow other data through the system. Interrupt prevent different data streams that can not use the same physical circuit and at the same time anyway.

            In addition to the two above variables NIC also has its own unique code, which means there's only one consisting of 12 diit code is often called a MAC (Media Access Control) addresses

 

Wireless

Unguided media transmits electromagnetic waves without using a physical conductor cable or optical fiber. A simple example is the radio waves such as microwaves, mobile wireless, and so forth. Media requires antennas for transmission and reception (transmitter and receiver). There are two types of transmission, Point-to-point (unidirectional) ie where the beam focused on a single target. Broadcast (omnidirectioanl) which is where the signal radiates in all directions and can be received by multiple antennas. Three kinds of frequency areas, among others:

a.       Microwave (microwave) 2-40 GHz

b.      Radio waves 30 Mhz - 1 Ghz

c.       infrared wavelengths

For media are not guided (unguided), the transmission and reception can be achieved by using an antenna. For transmission, antennas emit electromagnetic energy into the medium (usually air) and for the reception, the antenna picks up electromagnetic waves from the surrounding medium. Not guided transmission media (unguided) divided into four parts:

1.      Microwave Terrestrial (Earth's atmosphere)

Type microwave antenna is the most common dish 'dish'. Size is usually about 3 m in diameter. Focus the beam transmitting antenna short to reach the transmission line of sight toward the receiving antenna. Microwave antennas are usually placed at a certain height above the ground to extend the distance between the antenna and were able to penetrate the border. To achieve long distance transmission, it takes a microwave relay towers, and microwave link point to be installed at a certain distance.

Microwave system usability are the main long-haul telecommunications services, as an alternative to coaxial cable or fiber optic. Microwave facility requires fewer amplifiers or repeaters than coaxial cable at the same distance, but still require a line of sight transmission. Microwaves are generally used for the transmission of television or for the transmission of sound.

Users microwave was used to track the short dots between buildings. It can be used for network TV as closed or the data path between the Local Area Network. Short-haul Microwaves can also be used for special applications. For the purposes of the business is the path of microwaves to remote telecom facilities to the same city, through the local telephone company.

2.      Satellite Microwave

Satellite communication is a microwave relay station. Used to connect two or more transmitter / receiver microwave on earth, known as an earth station or ground station. Satellite receives transmissions on one frequency band (uplink), amplifier and repeat signals, and then transmits it to another frequency (downlink). A single orbiting satellite will operate in multiple frequency bands, called transponder channels, or simply transponders.

There are two common configurations for satellite communications are popular are:

a.       Satellites are used to provide point-to-point path between the two antennas of two earth stations

b.      Satellites provide communication between a transmitter and a number of earth station earth station receiver.

In order for satellite communications to function effectively, it is usually necessary to pay attention to the position of stationary orbit above the earth. Instead, each earth station should not be underlined of view all the time. For mrnjadi stationary satellites must have the same rotation period with the Earth's rotation period. Conformity occurs at an altitude of 35,784 km.

Two satellites using the same frequency band, when both are close enough, it will interfere with each other. To avoid this, the new standards require a 4 degrees of space.

Satellite communication is a revolution in communication technology and equally important view of the fiber optic. The most important applications for other satellites are:

a.       Distribution of television broadcast

b.      Transmission distance phone

c.       Private business network

Some characteristics of satellite communication can be described as follows:

·         due to long distances there is a delay spread (propagation delay) of approximately quarter of a second of a transmission from an earth station to be caught by another earth station. Besides emerging issues relating to error control and flow control.

·         microwave is a broadcasting facility, and this is their nature. Many diagnostic station can transmit to the satellite, and the transmissions from the satellite can be received by multiple stations.

3.      Radio Broadcast

The main differences between broadcast radio and microwave is, where are all the way radio (broadcast) while microwave direct (point-to-point). Therefore, the radio does not require a satellite dish antenna, and the antenna does not necessarily lead to the exact source of the broadcast
Radio is a term commonly used to capture the range of frequencies between 3 kHz to 300 GHz. We use the formal term not radio for VHF band and part of the UHF band: 30 MHz to 1 GHz. The range is also used for a number of applications of data networks.

Range of 30 MHz to 1 GHz is the effective range for broadcast communications. Unlike the case for low-frequency electromagnetic waves, the ionosphere is quite transparent to radio waves above 30 MHz. so the transmission is limited to line of sight, and the distance transmitter will not interfere with each other in the sense that there is no reflection of the atmosphere. Unlike higher frequency than zone microwaves, radio waves atenuansi little sensitive when it rains. Because of the long waves, radio waves relatively less experienced atenuansi.

The main source of interference to the radio is a multi-path interference. Reflections of earth, water, and natural or man-made objects can cause multi-path between the antennas. This effect was apparent when the TV receiver displays double images when the plane flew past.

4.      Infra Red

Infrared communication is achieved by using a transmitter / receiver (transceiver) that modulation of coherent light. Transceiver must be in the line of view and through the reflection of the light-colored surfaces such as ceiling. One important difference between the transmission of infrared and microwave radiation is infrared transmissions can not penetrate the wall, so that the problems of security and interference encountered in the microwave is not the case. Furthermore, there are no matters relating to the allocation of frequencies with infrared, because it does not need a license for it. In the mobile phone and PC, infrared media is used to transfer data, but with a standard or protocol that is separate IrDA protocol. Infrared light is light that is not visible. When viewed with a spectroscope the light radiation infrared light will appear on spektruk electromagnetic wavelength over the wavelength of red light.