The related words we hear often are analog phone lines, digital security, analog to digital adaptor and so on… what does all these mean?! In the world what we are present now everything is divided into analog or digital or a combination of both…

A signal is the transmission of datathat we constantly deal with during our daily routine life. From telephones to cellular devices, and music to computers, signals are very important. With the advent of modern technology, telephone and computers etc have became a necessity, and the cost of analog signal transmission has become not only expensive, but troublesome. Digital signals soon replaced analog because they are simply different and uniformed, and not severely altered by noise or distortion. Almost all electronic devices use digital signals, because they remain accurate in shape and amplitude. Digital signals provide better continuous delivery, and are preferred over analog signals.

Basic Definition:

An analog signal is a signal which is continuous over both the axis when we imagine a 2-d plane. A digital signal is a one which is continuous only over amplitude axis but not on time axis of a 2-d plane.

As a technology, analog is the process of taking an audio or video signal and translating it into electronic pulses. Digital on the other hand is breaking the signal into a binary format where the audio or video data is represented by a series of “1”s and “0”s.

In analog technology, a wave is used in its original form. So, for example, in an analog tape recorder, a signal is taken straight from the microphone and laid onto tape. The wave from the microphone is an analog wave, and therefore the wave on the tape is analog as well. That wave on the tape can be read, amplified and sent to a speaker to produce the sound.

In digital technology, the analog wave is sampled at some interval, and then turned into numbers that are stored in the digital device. On a CD, the sampling rate is 44,000 samples per second. So on a CD, there are 44,000 numbers stored per second of music. To hear the music analog voice signals are converted to digital signals for better clarity.

A digital signal can be referred to as the simple sampled version of an analog signal. We are here sampling the analog signal because its transmission takes much effort and it is easily subjected to noise. When it comes to digital signal transmission, as it is just a collection of 1’s and 0’s, by adding required parity bits we can transmit and receive it easily. Due to this easy transmission of the signal, digital signals are always preferable until we need the high clarity original signal.

An analog signal when sampled and rounded off the amplitudes to near by integers is a perfect example of digital signal generation.


            Analog lines also referred to as POTS (Plain Old Telephone Service), support standard phones, fax machines, and modems. These are the lines typically found in your home or small office.

How do you tell if the phone line is analog or digital? Look at the back of the telephone connected to it. If you see “complies with part 68, FCC Rules” and a Ringer Equivalence Number (REN), then the phone and the line are analog. Also, look at the phone’s dial pad. Are there multiple function keys? Do you need to dial “9” for an outside line? These are indicators that the phone and the line are digital.

The above shown is the old analog phone of ours where the signals used for transmission are a series of clock pulses with a constant time period. When we have to transmit a 1, we simply place our finger at 1 and turn the coil upto the end. Then we get a single clock pulse as output. If we wanted to transmit a 9, then we simply do the above procedure. But the output will be a 9 clock pulse signal. The coil here is called as magneto coil and used to transmit the numbers as we have done above.

The later phones like cordless and all comes under analog telecommunication itself. Now when we consider digital telecommunication part…

Digital cell phones are the second generation (2G) of cellular technology. They use the same radio technology as analog phones, but they use it in a different way. Analog systems do not fully utilize the signal between the phone and the cellular network — analog signals cannot be compressed and manipulated as easily as a true digital signal. This is the reason why many cable companies are switching to digital — so they can fit more channels within a given bandwidth.

Digital phones convert your voice into binary information (1s and 0s) and then compress it. This compression allows between three and 10 digital cell-phone calls to occupy the space of a single analog call. Many digital cellular systems rely on frequency-shift keying (FSK). FSK uses two frequencies, one for 1s and the other for 0s, alternating rapidly between the two to send digital information between the cell tower and the phone.


            Displaying a computer’s interface on an external monitor requires three pieces of dedicated hardware: the computer’s graphics card, which processes graphics data and prepares a digital or analog video signal for output; the connector, a cable between the computer and the monitor; and the monitor itself, which can use either an analog or a digital display.


The two main types of computer monitor connectors are VGA (video graphics array) and DVI (digital visual interface). While the cables have a similar appearance, VGA connectors can only carry a limited analog signal while DVI cables carry the added data of a digital signal. Individual monitors can include input ports for VGA, DVI or both. Computer makers and third-party manufacturers also produce cables to convert one video type to another, though these converters simply change the shape of the port, not the nature of the signal.

Display Types

Older computer monitors include CRT, or cathode ray tube, displays. These displays use analog technology and always include an analog VGA port for signal input. The other major type of computer display is LCD (liquid crystal display). LCD monitors—including LED monitors, which use light-emitting diode backlighting—are fully digital. However, LCD monitors often include both VGA and DVI input ports so that they are compatible with both types of cables. When a VGA cable is on an LCD monitor, the monitor displays the lower-quality analog image.

Display Technology

Analog CRT displays function in much the same way as a traditional non-flat screen television set. They use an electron gun to scan the rear of the display screen and continually produce an array of colors to produce the moving image. LCD displays contain liquid crystals that are electronically tuned to display a specific color within each tiny pixel. A backlight, either fluorescent or LED, shines through, producing the color image.


The chief advantage of digital monitors over analog is their greater resolution. VGA technology limits screen resolution to 640 x 480 pixels, for a total of 307,200 pixels. DVI, on the other hand, can display up to 1,920 x 1,200 resolution with 2,304,000 pixels, more than seven times greater than VGA resolution. Only DVI monitors can take advantage of the high-powered graphics cards in modern computers, or the high resolution of Blue-ray movies and high-definition Internet content.

* More information on this topic will be posted in the future articles.

Posted By

Gopi Chand

(3/4 ECE MGIT)

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