What is difference between modulator and demodulator?

Answer 1

Modulation is used when information is available in analog form that varies the frequency and/or amplitude of a lower frequency wave, depending on the information it carries. The role of modulation is to place this information onto a carrier frequency that can be transmitted more readily and with least loss of information. There are three fundamental types of modulation - frequency modulation, amplitude modulation and phase modulation. In each of these, a carrier frequency is modulated by a lower frequency, to form a modulated carrier wave. A modulator modulates the carrier frequency, while a demodulator detects the modulation on the carrier wave and recovers the original lower frequency waveform at the destination. For many years the modulated carrier wave was converted to a radio signal. Now it is often an electrical signal which is sent down a teleohone line; the information is usually a set of pulses going between computers. When computers are connected to each other in a two-way conversation, the MOdulator and DEModulator are combined into a single device called a MODEM.

Answer 2

An RF modulator takes signal from an analog input such as Red/White/Yellow RCA, and '"Modulates" the signal into something that is usable by Coaxial.

An RF De-Modulator does the opposite, it takes the modulated RF signal from a Coaxial cable and decodes it if you will into an analog input such as RCA or SVideo.

Modulator- RCA to Coax

DeModulator- Coax to RCA