Question

modem

Answer 1

Modem term is made from two words (1) Modulator and (2) Demodulator. Therefore, it is a device (may be hardware or software) that works as a modulator as well as a demodulator.

So, now what is modulator? The modulator is used to change the properties (can be frequency, phase, amplitude, etc.) of an information signal (can be in the form of a digital signal or analog signal or in any other form) by imposing it to another signal (termed as the carrier).

The demodulator is the part of modem that performs the reverse of the modulator, that is it converts the signal into its original form.

Let's consider an example, that we have a signal of frequency 2Hz that needs to transmit from one place to another. Then, simply sending it may cause it to get affected by interference, due to small signal to noise ratio. So, the modulator part of the modem at the sender end uses its high-frequency carrier signal to change the information signal frequency. Therefore, low-frequency information signal gets converted into a high-frequency signal, and hence the high signal to noise ratio and less susceptible to interference. Similarly, the demodulator part of the modem at the receiver end perform the reverse of the modulator operation. Therefore, it converts the high-frequency signal into low-frequency by imposing it to same carrier signal and gets the original information signal.

Conclusion:

Therefore, the modem is a device that performs the modulation and demodulation of an information signal by imposing it to a predecided carrier signal, so that the transmission of the information signal becomes easy. Also, at the destination, it enables us to get the original information signal.