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1. Explain the purpose of converting analog signals to digital and give an example.

Analog signals can assume any value; noise is interpreted as being part of the original signal. For example, when you listen to a LP record, you hear noise because the needle is analog and thus don’t know the difference from the music originally recorded from the noise inserted by dust or cracks.

Digital systems, on the other hand, can only understand two numbers, zero and one. Anything different from this is discarded. That’s why you won’t hear any unwanted noise when listening to an audio CD, even if you played it thousands of times before (actually depending on your sound system you can hear some noise when playing audio CDs, but this noise, called white noise, isn’t produced by the CD media, but by the CD player, amplifier or cables used, and is introduced in the audio path after the digital data found on the CD was already converted back to analog – as you see, the problem lies in the analog part).

Whenever we need the analog signal back, the opposite conversion – digital-to-analog, which is done by a circuit called DAC, Digital-to-Analog Converter – is needed. When you play an audio CD, what the CD player is doing is reading digital information stored on the disc and converting it back to analog so you can hear the music.

2. Explain the purpose of converting digital data to analog and give an example.

A device that converts the digital signals produced by terminals and computer into the analog signals that telephone circuits are designed to carry. Despite the availability of several all-digital transmission networks, the analog telephone network remains the most readily available facility for voice and data transmission. Since terminals and computers transmit data using digital signaling, whereas telephone circuits are designed to transmit analog signals used to convey human speech, a...