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Signal Theory

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BTEC National Certificate for IT Practitioners Unit 8 Communication Technologies Assignment 1 In this assignment I am going to describes different types of communication devices. For example Switches, Routers, etc. Then I am going to explain the principles of signal theory. After this I will look at difference methods of electronic communication and transmission used. Communication Devices Switches - These are mainly used for local area networks (LAN). The reason behind this is that they can be used to bridge a lot of computers together. They do look like hubs but they can vary in speed. They are more intelligent due to the fact that they can send out packets from a set port. There is advantage of using a network switch, they can be used with an Ethernet cable or a fibre optic cable and they still will work perfectly fine. When connecting a router or a server in an LAN or WAN network it is slightly easier because you would just need one cable which would mostly need to a fibre optic cable, so you can get the maximum rate of transfer speed. Routers - They are mainly used for connecting one network to another. They are meant for handling information and forwarding to another network connected to the router. You can either connect using wireless or a cable. Normally an Ethernet cable is used to connect the computer networks. Hubs - Also known as a concentrator or a multiport repeater. Used in a star or a hierarchical network setup to connect the station or the cable segments. There are two main types of hubs: passive & active. Active takes the incoming traffic, amplifies the signal and then forwards it all the ports. In a passive hub it simply divides the incoming traffic and forwards it. A hub can be used to manage and allow individual port configuration and traffic. Hubs operate on the physical layer of the OSI model and they are protocol transparent. ...read more.


IEEE - Institute of Electrical and Electronics Engineers allows the development of "Electro Technology" which in other words applies to electricity applied to technology. Societies like the IEEE Computer Society are subsidiaries of the IEEE itself. This standards organization also publishes journals. Devices such as digital camera need set amount of bandwidth speed so it uses a IEEE plug. Any device that uses the IEEE standard uses a twisted pair cable. Signalling Standards NRZ- It stands for Non Return to Zero. It is a binary code normally used for slow speed synchronous and asynchronous transmission interfaces. Ones is represented as a small voltage and zero is negative voltages. They are transmitted by either by set or constant DC voltages. It also uses additional synchronisation so it dose not lose any bits in the process. NRZ-L - Non Return to Zero Level is similar to NRZ, but it not a binary code. Same as NRZ one is represented as small voltage, but zero is also represented as a small voltage but it is not as big voltage as one, Therefore it allows more data to be send without a lot of signal change. NRZ-M - Non Return to Zero Mark again similar to NRZ, but one is actually represented by a change in physical state and zero is represented as change in physical state. This basically means that there is no voltage when there is no change in physical state. RS-232 - This standard applies to serial data transfer such as the 9 pin serial connecters which are commonly used on a computer motherboard. The data is sent in as time series of bits. Synchronous & Asynchronous is both supported by this standard. This standard and states the number of control circuits that can be or need to be used to connect the DCE & DTE terminal with one another. Data and control circuits which are signalled from a DTE connected to a DCE or vice versa will always flow and operate in one direction this is called half duplex. ...read more.


Data Transmission Modes & Methods There are three different ways transmission can take place. Data transmits either using simplex, half duplex or full duplex mode. There are two different ways how data is transmitted. Data can be transmitted via serial or via parallel transmission. Simplex Simplex data can only travel in one direction. Television and radio broadcasting are example of simplex. Fibre optic works with simplex mode. Simplex is good for satellite communications. TV signal is the proof that satellite communication is good because the transmission is good and clear. Simplex is rarely used for computer based telecommunications. Half Duplex Half duplex data can travel both ways but only in one direction. Coaxial cable works in half duplex mode. Radio is a example of half duplex because the signal reaches the destination and comes back to the original source. Communication between networks also works at half duplex. If a node is transmitting a message and another node wants to transmit it has to wait till the token ring comes back. Full Duplex In full duplex data can travel in both directions and at the same time. The bandwidth is divided in both directions. UTP/STP mediums work at full duplex. For example Bluetooth is a full duplex because data can be received and sent by both devices. Another example is landline telephone because both end of the phone can speak and listen to each other. Serial Transmission In serial transmission one bit is sent at a time. It is good for communication between several participants. Serial transmission is slow. When the data is sent it is dissembled by the source and reassembled by the receiver. Parallel Transmission Parallel transmission is when every bit is sent simultaneously but using separate wire. Basically when data is parallel channel transmitted for i.e. 8 bits or a byte everything is sent simultaneously therefore it's faster than serial because serial channel would send the 8 bits or byte one by one. Most common example is communication between a printer and the computer. ?? ?? ?? ?? Anas Patel Assignment 1 Anas Patel Assignment 1 Anas Patel Assignment 1 ...read more.

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