Electronic Devices: How Analog And Digital Recording Works

How different devices record and store digital and analog data, and why they're different.

Cassette tape recorders, VCRs, Floppy drives and CD-ROM drives all have one thing in common: they all record information. Whether it is sound, images or data, these devices store information for later use. The major difference between the devices is how they store and record our favorite music, movies or irreplaceable data.

Computers operate on a digital format. The word digital comes from the base word of digit, which is any form of the Hindu-Arabic figures from zero to nine. A digital format comes from using the numbers 1 and 0, or on (represented by one) and off (represented by zero). These two numbers are binary digits. A Transistor, the miracle of the last century, electrically produces binary digits. A transistor can only turn electricity on, which is equal to one, and off which is equal to zero.

A basic digital code is as follows: 00001010. This is how computers represent all information, with more complex codes for more complex pieces of information. A song or an image, such as a movie, can contain literally millions of these small bits of code or information. The information is stored as a binary digit of a 0 and 1. These binary digit codes are then burned, using a laser beam, into the chemical layer of a CD-ROM. On a Floppy drive disk, small magnetic iron particles are realigned in such a way so they can store the information also as a 1 and 0.



Both of these devices are digital recorders. They use different methods for storage but the information is still the same, binary digit numbers of 1 and 0.

Analog recording stores information and does so in a completely different way. An analog signal is variable in other words, the voltage or current moves like a wave. The stronger the input signal to be recorded then the greater the intensity of the wave.

Think of this wave like the wind blowing across a small pool of water. The stronger the wind blows then the waves it creates is also larger. Analog signals act in much the same way. The greater the intensity of the input signals, the higher the peaks of the waveform. The waveform can also be positive in voltage, greater than zero, or negative in voltage, less than zero. Digital can only be a one or a zero, never in between.

Sound recorded from a microphone originates as an analog signal. This is true for even your computer microphone. The computer uses a component called a digital to analog converter named a DAC, and an analog to digital converter, ADC.

Let us say you want to record your voice through your computer's microphone. As you speak the ADC works to store the waveform sound into a digital format. When you play music back on the computer the DAC works to transform the digital 1 and 0 to a waveform that can be heard on your speakers.

The storage medium for an analog signal is generally a ribbon or tape. The recording tape has a covering of small iron particles on the surface. These particles resemble very small compasses with all of the little needles pointing in some random direction. When a magnetic field passes across the tape, such as the recording head in a VCR or cassette tape recorder, the iron particles realign. This realignment of the small particles actually stores the waveform of the sound. This transfer is identical to the sound made through a microphone.

Analog signals transfer in their original state as a waveform to magnetic tape. These waveform signals are easy to alter in their intensity by adjusting the volume and tone. The waveform is the same as when you speak into the microphone, and the recording head realigns the iron particles on the tape to store the information.

Playback from an analog recording is merely the amplification of the waveform from the magnetic iron particles on the storage tape. No real conversion to the waveform sound is needed as in the digital recordings from a computer.

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