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Video signals are usually encoded into binary digit (0, 1) or seven digit pulse-code modulation (PCM), which is a method used to digitally represent original video signal. . The video signal converted to binary digit PCM at the point of origin can be then transmitted over existing telephone cable or wire directly to the destination
ASTEC UM 1286 UHF modulator, top cover taken off. An RF modulator (radio frequency modulator) is an electronic device used to convert signals from devices such as media players, VCRs and game consoles to a format that can be handled by a device designed to receive a modulated RF input, such as a radio or television receiver.
It was used as a local oscillator in some radar receivers and a modulator in microwave transmitters in the 1950s and 1960s, but is now obsolete, replaced by semiconductor microwave devices. In the reflex klystron the electron beam passes through a single resonant cavity. The electrons are fired into one end of the tube by an electron gun. After ...
A modulator is a device or circuit that performs modulation. A demodulator (sometimes detector ) is a circuit that performs demodulation , the inverse of modulation. A modem (from mod ulator– dem odulator), used in bidirectional communication, can perform both operations.
These terms are traditionally used in connection with radio receivers, but many other systems use many kinds of demodulators. For example, in a modem , which is a contraction of the terms modulator /demodulator, a demodulator is used to extract a serial digital data stream from a carrier signal which is used to carry it through a telephone line ...
Analogue television receivers using system M: 41.25 MHz (audio) and 45.75 MHz (video). Note, the channel is flipped over in the conversion process in an intercarrier system, so the audio IF is lower than the video IF. Also, there is no audio local oscillator; the injected video carrier serves that purpose.
FM receivers employ a special detector for FM signals and exhibit a phenomenon known as the capture effect, in which the tuner "captures" the stronger of two stations on the same frequency while rejecting the other (compare this with a similar situation on an AM receiver, where both stations can be heard simultaneously).
A video decoder It transforms video packets into a sequence of pictures, which are displayed by the TV monitor. An audio decoder It decompresses the audio bit-stream. Different audio modes are usually supported by the DTV receiver: mono and dual channel, stereo, and joint stereo. A data decoder. Graphics Processor