Data modulation is a process that converts analog signals into digital signals and digital signals into analog signals. Computers store and process data in digital format. Data modulation allows computers to store and process analog signals.
To send information signal in long distances, we use modulation. It usually involves varying one waveform in relation to another waveform.
Let’s take a simple example. When you record and play an audio clip, the following happens.
You use a microphone to record the audio clip. The microphone sends your voice to the computer. Since the human voice consists of analog signals, the computer converts the received voice into digital signals before processing and storing them onto the hard disk.
When you play the record, the computer reads digital signals from the hard disk and converts them into analog signals before sending them to the speaker.
We can use data modulation method within and outside the computer. It allows computers to send digital signals on a media that can only carry analog signals. It converts signal so they become suitable for transport on a communication path.
Telephone lines only carry analog signals, with data modulation the same telephone lines can also be use to provide the internet facility. We can use a modem to provide the internet facility through telephone lines. A modem can act as both a modulator and a demodulator.
A modem connects a computer to the ISP network via a telephone line. It modulates digital signals into analog signals at the transmitting end, then demodulates analog signals into digital signals at the receiving end.
Types of Modulation :
1. Amplitude Modulation :
It is a process to change the amplitude of carrier signal according to digital signal having information.
2. Frequency Modulation :
It is a process to change the frequency of carrier signal according to digital signal having information.
3. Phase Modulation :
It is a process to change the phase of carrier signal according to digital signal having information.
Data Transmission Services
We use data transmission service to transmit data from one place to another, data transmission providers usually provides this service.
Example (Indian Service Providers) :
- MTNL (Mahanagar Telephone Nigam Limited)
- VSNL (Videsh Sanchar Nigam Limited)
- BSNL (Bharat Sanchar Nigam Limited)
Data Transmission Service Technology
1. Dial up lines :
Dial up lines is a form of Internet access that uses the facilities of the public switched telephone network (PSTN) to establish a connection to an Internet service provider (ISP) by dialing a telephone number on a conventional telephone line. Dial-up connections use modems to decode audio signals into data to send to a router or computer, and to encode signals from the latter two devices to send to another modem.
It is used by dialing the number like telephone and it is used to already established telephone lines over the world. Dial-up lines are sometimes called switched lines and broad band technique is also used by dial up lines.
2. Leased Lines :
A leased line is used to connect the two locations for voice and data transmission. It is also called dedicated line and it makes transmission possible near and far. It is also use as a reserved circuit between two points. Generally, leased lines are used by businesses to connect on distant branch offices, because it makes sure to provide higher quality bandwidth in network traffic.
3. ISDN (Integrated services digital network) :
We use ISDN to transmit voice, video, images and data trhough switched telephone network. The key feature of ISDN is that it integrates speech and data on the same lines, adding features that were not available in the classic telephone system.
ISDN is a circuit-switched telephone network system which also provides access to packet switched networks, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in potentially better voice quality than an analog phone can provide. You don’t need a modem to transmit signal in ISDN because data transmits in digital form.
4. NIC (Network Interface Card) :
NIC is a harware componenet that allow computers to communicate over a network, in which computers sends and receives data packets under a network protocol.
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