# Data Signals

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1. The latency or delay defines how long it takes for an entire message to completely arrive at the destination from the time the first bit is sent out from the source.

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2. It can be said that the Latency is made of four components: propagation time, transmission time, queuing time and processing delay. Latency =propagation time +transmission time +queuing time + processing delay

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3. The throughput is the actual measurement of data that can be sent over network. It is different from Bandwidth which is the maximum amount of data that can travel through a network.

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4. The term bandwidth refers to the maximum amount of data that a channel can transmit. For example if the bandwidth of a Fast Ethernet network is a maximum of 100 Mbps then this network can send 100 Mbps or less depending on various factors.

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5. The time needed for each intermediate or end device to hold the message before it can be processed. The queuing time is not constant as it changes with the load imposed on the network.

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6. The transmission time, is the amount of time from the beginning until the end of a message transmission. It depends on the size of the message and the bandwidth of the channel. Transmission time =Message size / Bandwidth

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7. Nibble refers to the half of an eight-bit byte or four binary digits. Byte is a group of bits (8 bits) used to represent a character. A byte is considered as the basic unit of measuring memory size in computer.

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8. The sine wave is the most fundamental form of a periodic analog signal. A periodic signal completes a pattern within a measurable time frame, called a period, and repeats that pattern over subsequent identical periods.

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9. Bandwidth = Highest frequency - Lowest frequency. In this case, bandwidth will be equal to 900Hz-100 Hz i.e. 800Hz.

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10. Data rate depends on three factors: 1. The bandwidth available 2. The level of the signal in use 3. The quality of the channel (the level of noise)

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11. The bit length is the distance one bit occupies on the transmission medium. It is given by the formula: Propagation speed * bit duration.

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12. Typically the source of data is a computer, but it can be any other electronic equipment such as telephone handset, video camera, etc, which can generate data for transmission to some destination.

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13. As data cannot be sent in its native form, it is necessary to convert it into signal. This is performed with the help of a transmitter such as modem.

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14. ASCII code is used to represent digital data. In ASCII code, each character is represented by a 7-bit code.

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15. The bit interval is the time required to send one single bit. It, along with bit rate, is used to describe the digital signals.

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16. The bit rate is the number of bit interval per second. This mean that the bit rate is the number of bits send in one second, usually expressed in bits per second.

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17. Base-band signaling is defined as one that uses digital signaling, which is inserted in the transmission channel as voltage pulses.

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18. Attenuation is the loss of signal's energy due to resistance of the medium. It is not the same as Distortion which is the alteration of the signal due to different propagation speeds.

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19. Distortion is the change in the waveform of the signal due to noise. It is the alteration of the signal due to differing propagation speeds of each of the frequencies.

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20. When signals at different frequencies share the same transmission medium, the result may be intermodulation noise. Signals at a frequency that is the sum or difference of original frequencies or multiples of those frequencies will be produced.

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