Signal definition

 

Introduction to Communication and Networking

What is Signal?

A signal is an electromagnetic or electrical current that is used for carrying data from one

system or network to another. The signal is a function that conveys information about a

phenomenon.

In electronics and telecommunications, it refers to any time-varying voltage that is an

electromagnetic wave which carries information. A signal can also be defined as an

observable change in quality such as quantity. There are two main types of signals: Analog

signal and Digital signal.

Analog Signal

Analog signal is a continuous signal in which one time-varying quantity represents another

time-based variable. These kind of signals works with physical values and natural phenomena

such as earthquake, frequency, volcano, speed of wind, weight, lighting, etc.

Here, are essential characteristics of Analog Signal

 These type of electronic signals are time-varying

 Minimum and maximum values which is either positive or negative.

 It can be either periodic or non-periodic.

 Analog Signal works on continuous data.

 The accuracy of the analog signal is not high when compared to the digital signal.

 It helps you to measure natural or physical values.

 Analog signal output form is like Curve, Line, or Graph, so it may not be meaningful

to all.

Advantages of Analog Signals

Here, are pros/benefits of Analog Signals

 Easier in processing

 Best suited for audio and video transmission.

 It has a low cost and is portable.

 It has a much higher density so that it can present more refined information.

 Not necessary to buy a new graphics board.

 Uses less bandwidth than digital sounds

 Provide more accurate representation .

 Low availability of models with digital interfaces.

 Recording analog sound on tape is quite expensive if the tape is damaged

 It offers limitations in editing

 Tape is becoming hard to find

 It is quite difficult to synchronize analog sound

 Quality is easily lost

 Data can become corrupted

 Plenty of recording devices and formats which can become confusing to store a digital 

signal

 Digital sounds can cut an analog sound wave which means that you can’t get a perfect 

reproduction of a sound

 Offers poor multi-user interfaces

Digital Signal

A digital signal is a signal that is used to represent data as a sequence of separate values at 

any point in time. It can only take on one of a fixed number of values. This type of signal 

represents a real number within a constant range of values. Now, let’s learn some key 

difference between Digital and Analog signals.

Here, are essential characteristics of Digital signals

 Digital signals are time separated signals.

 This type of electronic l signals can be processed and transmitted better compared to 

analog signal.

 Digital signals are versatile, so it is widely used.

 The accuracy of the digital signal is better than that of the analog signal.

Advantages of Digital Signals

Here, are pros/advantages of Digital Signals:

 Digital data can be easily compressed.

 Any information in the digital form can be encrypted.

 Equipment that uses digital signals is more common and less expensive.

 Digital signal makes running instruments free from observation errors like parallax 

and approximation errors.

 A lot of editing tools are available

 You can edit the sound without altering the original copy

 Easy to transmit the data over networks

Disadvantages of Digital Signals

 Sampling may cause loss of information.

 A/D and D/A demands mixed-signal hardware

 Processor speed is limited

 Develop quantization and round-off errors

 It requires greater bandwidth

 Systems and processing is more complex.

TIME 

 It is the natural form of a sound.

Difference Between Analog and Digital Signal

Analog signal 

An analog signal is a continuous signal that

represents physical measurements.

Digital signals are time separated signals

which are generated using digital modulation.

It is denoted by sine waves It is denoted by square waves

It uses a continuous range of values that

help you to represent information.

Digital signal uses discrete 0 and 1 to

represent information.

Temperature sensors, FM radio signals,

Photocells, Light sensor, Resistive touch

screen are examples of Analog signals.

Computers, CDs, DVDs are some examples of

Digital signal.

The analog signal bandwidth is low The digital signal bandwidth is high.

Analog signals are deteriorated by noise

throughout transmission as well as

write/read cycle.

Relatively a noise-immune system without

deterioration during the transmission process

and write/read cycle.

Analog hardware never offers flexible

implementation.

Digital hardware offers flexibility in

implementation.

It is suited for audio and video transmission. It is suited for Computing and digital

electronics.

Processing can be done in real-time and

consumes lesser bandwidth compared to a

digital signal.

It never gives a guarantee that digital signal

processing can be performed in real time.

Analog instruments usually have s scale

which is cramped at lower end and gives

considerable observational errors.

Digital instruments never cause any kind of

observational errors.

Analog signal doesn’t offer any fixed range. Digital signal has a finite number, i.e., 0 and 1.

What is Transmission?

Transmission is the action of transferring or moving something from one position or person

to another. It is a mechanism of transferring data between two devices connected using a

network. It is also called communication Mode.

Serial and Parallel Data Transmission

Data transmission can occur in two modes (methods), either serial or parallel.

Serial data transmission

In Serial Transmission, data is sent bit by bit from one computer to another in bidirection

where each bit has its clock pulse rate. Eight bits are transferred at a time having a start and

stop bit (usually known as a Parity bit), i.e. 0 and 1 respectively. For transmitting data to a

longer distance, serial data cables are used. However, the data transferred in the serial

transmission is in proper order. It consists of a D-shaped 9 pin cable that connects the data in

series. Serial Transmission has two subclasses synchronous and asynchronous. In

asynchronous transmission, an extra bit is added to each byte so that the receiver is alert

about the arrival of new data. Usually, 0 is a start bit, and 1 is the stop bit. In synchronous

transmission, no extra bit is added rather the data transferred in the form of frames which

contains multiple bytes. The serial transmission system would not be able to work without

installing hardware at the sending and receiving. The hardware residing in the sending and

receiving end is capable of converting the data from the parallel mode (used in the device) to

the serial mode (used in the wires). 

Here are cons/drawback of Analog Signals:

 Analog tends to have a lower quality signal than digital.

 The cables are sensitive to external influences.

 The cost of the Analog wire is high and not easily portable

Uses of serial transmission

 Transmission to another computer or to external devices

 Medium to long distances

 Universal Serial Bus (USB)

Advantages:

 It is cost-effective

 It is appropriate for long-distance communication

 More reliable

Disadvantages

 Data transmission rate is low.

 Throughput relies on the bit rate.

Parallel data transmission

In Parallel Transmission, various bits are sent together simultaneously with a single clock

pulse. It is a fast way to transmit as it uses many input/output lines for transferring the data.

Furthermore, it is advantageous because it conforms to the underlying hardware also, as the

electronic devices like computer and communication hardware uses parallel circuitry

internally. This is a reason the parallel interface complements the internal hardware well. The

installation and troubleshooting is easier in parallel transmission system due to its placement

in a single physical cable.

Parallel Transmission uses a 25 pin port having 17 signal lines and 8 ground lines. The 17

signal lines are further divided as  4 lines that initiate handshaking,  Status lines used to

communicate and notify errors and  8 to transfer data. Despite the speed of the data, the

parallel transmission has a limitation called skew where bits could travel in quite different

speeds over the wires.

Uses of parallel transmission

 Fast transmission within a computer system

 Short distances

 Integrated Circuits (IC), Busses

Advantages:

 Transmits data at a higher speed.

 Suits better for short-distance communication.

 Set of bits are transferred simultaneously.

Disadvantages:

 It is a costly transmission system.

 In order to transmit the data over long ranges, the thickness of the wire has to be

increased to diminish signal degradation.

 There are multiple communication channels required.