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A Digital TV Tuner
Devices that pick up radio transmissions need a tuner. This can be a stand-alone device or more often it is built into a larger system Examples of tuners can be found in ...
- TV Sets
- Satellite Receivers
- Mobile Phones
- SatNav receivers
What the tuner does ...
- It amplifies the weak radio signals.
- It selects the wanted station and filters out all the others.
- It demodulates the radio signal giving audio, video or data signals.
Quite a lot of power is needed to drive loudspeakers. A small radio might have a 0.25 Watt amplifier. Some TV surround sound systems have powers up to 100 Watts. The function of the amplifier is to increase the small input signal up to a level sufficient to drive the loudspeakers.
Amplifiers need to work well for the whole range of Audio Frequencies.
- 20 to 20000 Hz is needed for top quality audio, typical in entertainment systems.
- 20 to 15000 Hz is the range transmitted by FM radio stations. This still sounds good.
- 50 to 4000 Hz is typical for AM radio. This sounds a lot less nice.
- 300 to 3000 Hz is the minimum needed for clear voice communication. Telephone calls use this frequency range.
- This is an input transducer.
- It converts energy in the form of pressure waves in air into electrical energy.
- The voltage produced by the microphone is proportional to the air pressure.
Woofer, Midrange and Tweeter Loudspeakers
- This is an output transducer.
- It converts electrical energy into movements of a paper cone which produces pressure waves in the air.
- The air pressure produced by the loudspeaker is proportional to the voltage of the electrical signal.
MP3 or similar Players
Low Cost MP3 Player
- Music is stored digitally.
- This means it is stored in the memory chips as binary zeros and ones.
- To play pack the music, the digital data must be converted into an analogue signal.
- A digital to analogue converter (DAC) does this.
- The analogue music signal is amplified and fed to the loudspeakers.
CD and DVD Players
Audio CD Player
- Compact disks, digital versatile disks and blu-ray disks all contain digital data.
- A DAC or digital to analogue converter produces analogue audio and video signals.
- The audio is amplified and sent to loudspeakers or headphones.
- The video signal is sent to the display screen.
CD and DVD Recorders
- To record audio and video, the analogue signals must be converted into digital.
- An analogue to digital converter (ADC) does this conversion.
- The digital data (zeros and ones) is recorded onto the CD or DVD.
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