Term
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Definition
| Movement of data from one place to another via a transmitter and receiver. |
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Term
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Definition
| Single bits are sent one after another along a single wire by varying the voltage. |
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Term
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Definition
| Electromagnetic waves are guided along a physical path (e.g twisted pairs, coaxial cables, optic fibres). |
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Term
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Definition
| Not guided to a receiver (e.g radio waves). |
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Term
| Problems with guided and unguided media |
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Definition
| The signal decreases in strength with distance. If this is not corrected, the data encoded in the signal will not be recoverable. |
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Term
| Parallel data transmission |
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Definition
| Bits are sent down several wires simultaneously. |
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Term
| Why is serial data transmission used over long distance? |
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Definition
| Requires only 1 signal path each way so saves on cost of cabling. It is also easier to regenerate the signal. |
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Term
| Why is parallel data transmission used over short distance? |
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Definition
| It is difficult to keep the voltages on the eight wires in line with each other beyond a certain distance. It is expensive to run over a long distance. |
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Term
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Definition
| The rate at which signals on a wire may change. |
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Term
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Definition
| One signal change per second |
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Term
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Definition
| The number of bits transmitted per second. It is possible to transmit more then 1 bit per signal change if multiple voltage levels are used to encode bits. |
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Term
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Definition
| Measured in hertz. For a transmission medium (i.e copper) this is the range of signal frequencies that it may transmit. It is a measure of how fast data may be transmitted. |
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Term
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Definition
| The time delay that can occur between something being initiated and the moment it's first effect begins. |
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Term
| Asynchronous serial data transmission |
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Definition
| The transmitter and receiver are not synchronised. The arrival of data cannot be predicted by the receiver; a start bit is used to signal the arrival of data and to synchronise the transmitter and receiver temporarily. |
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Term
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Definition
| A bit appended to data in order to check for errors. Set to 1 or 0 in order to make the number of 1s or 0s an even or odd number (even or odd parity). The receiver calculates its own parity bit and checks it against the parity bit appended by the transmitter. If they are different an error has occurred. |
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Term
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Definition
| A set of pre-arranged signals/rules to be used for data exchange between computers to ensure the communication is successful and understood by both receiver and transmitter. |
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Term
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Definition
| The sending and receiving devices exchange signals to establish that the receiving device is ready to receive. Handshaking can inform that the sending device is sending (start bit) or the receiver has received the data and is ready to receive again (stop bit). |
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Term
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Definition
| A system that uses a single data channel in which the whole bandwidth of the transmission medium is dedicated to one data channel at a time. Used in short distances such as LANs to offer high performance at low cost. |
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Term
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Definition
| A multiple channel system in which the bandwidth of the transmission medium carries several data streams at the same time. |
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Term
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Definition
| The shape, layout, configuration or structure of the connections that connect devices to the network. |
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Term
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Definition
| Two LANs combined are said to be internetworked. The internet is an example of this. |
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Term
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Definition
| A device used to connect networks that use two different protocols |
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