There are two types of signals which are used for data transmission, Digital signals and Analog signals. A digital signal is a physical signal that is used to represent a series of 0's and 1's. So this type of digital signals are particularly appropriate for computers to use. An analog signal uses modulations in signal to communicate information. It is mainly useful for wave data like “sound wavesâ€. Analog signals are used in your land-line phone lines and speakers of sound system.
So far as the matter of communications between computers concerned, we use the telephone system for at least part of the channels. A device is required to translate language between the analog phone line and the digital computer. The devices which can translate these languages are called modems. Modems usually use the Modulate/Demodulate technology. (Modulation is the process of varying one or more properties of a periodic waveforms while Demodulation is an electronic circuit used for bearing-information signal from a modulated carrier wave). The modem modulates a digital signal from the computer into an analog to send data out over the phone line. Followed by an incoming signal which, demodulates the analog signal into a digital signal.
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Transmission Rate - The transmission rate speaks about the communications between a modem and a computer at multiplicity of transmission rates. The modem has the ability to transmit information signals over a control channel at any point of transmission rates. However, confusion occurs when it comes to calculation of transmission rate of a modem. There is a term for this entire process called ‘Throughput’. Here it calculates the total amount of data moving at a certain point of time. Hence the modem is the only element of the process for moving data. If you put a faster modem it will not speed up your data transfers.
| Throughput (Kbps) |
14.4 | 28.8 | 50 | ISDN 128 |
256 | Cable 1544 |
ADSL 8000 |
|---|---|---|---|---|---|---|---|
| File Size | Download Time | ||||||
| 1 MB | 9.26 min |
4.63 min |
2.6 min |
1 min |
31.25 s |
5.18 s |
1 s |
| 10 MB | 1.54 hr |
46.3 min |
26.6 min |
10.4 min |
5.2 min |
51.8 s |
10 s |
| 1000 MB (gigabyte) |
6.4 days |
3.2 days |
1.85 days |
17.4 hr |
8.6 hr |
1.4 hr |
16.6 min |
There are two different types of processes in which data transfers are measured. They are Digital process and Analog process. In the first process the rate of digital transmission is measured in bits per second (bps) whereas the common rates for regular modems are 28.8 Kbps, 33.6 Kbps, and 56 Kbps (K stands for thousand). In the second process the analog side is measured in Baud, where 1 baud is one change in the signal per second. A protocol describes all the information exchanged and its order. The names of the protocols are in the form of v.##, so that you will be able to finds inscriptions like v.25bis, v.34, and v.120. Some protocols are more stable or faster than others at certain tasks.
