Network Topology & Protocols

Standards and Protocols:

Standards and protocols are required to govern the physical and logical connections between terminals, Computers and other equipment. They are vital for data communications and computer networking.

Typically, standard fall into two groups official standards (from national standards bodies) and defacto standards established by common usage.

An early official standard was the EIA RS232 for data transfer over wires (Electronic Industries Association Recommended Standard).

Network Topology:

The topology defines how the devices (Computers, printers… etc) are connected and how the data flows from one device to another. There are two conventions while representing the topologies. The physical topology defines how the devices are physically wired. The logical topology defines how the data flows from one device to another.

Broadly categorized into i) Bus ii) Ring iii) Star iv) Mesh

Data Transmission: Analog & Digital

Data Transmission: Analog and Digital

Analog Transmission:

Dominated the last 100 years and is here for a while yet networks designers made use of the existing telephone network which was aimed at voice transmission. This is actually very poor for computer networking for example, 2 computers connected by a direct cable can achieve a data rate of up to 100Mbps with very low error rate using phone lines, 56Kbps is the maximum transmission speed with a relatively high error rate. It is approximately 10 orders of magnitude worse the cost of bus ticket town versus a moon landing is same order of magnitude

Modems:

Data Communication and Computer Networks

Data Communication and Computer Networks

Data Communications has an ancient history, as people have always had an interest in communication with each other. Different methods have been used and associated with each method are various advantages and disadvantages. A major problem with communications is ensuring that the receiver gets the message sent by the transmitter.

DSP Using MATLAB

1. DFT of given sequence using MATLAB

Fourier analysis is a family of mathematical techniques, all based on decomposing signals into sinusoids. The discrete Fourier transform (DFT) is the family member used with digitized signals. A signal can be either continuous or discrete, and it can be either periodic or Aperiodic. The combination of these two features generates the four categories, described below

REPRESENTATION OF BASIC SIGNALS USING MATLAB

Sinusoidal Signal, Unit Impulse, Unit Step, Ramp, Sawtooth Wave Forms

Generate Sinusoidal signal

clear all;

close all;

clc;

N = input('Enter the number of cycles ...:: '); t = 0:0.05:N;

x = sin(2*pi*t);

Introduction to MATLAB

Introduction to MATLAB

MATLAB is a software package for high performance numerical computation and visualization provides an interactive environment with hundreds of built in functions for technical computation, graphics and animation. The MATLAB name stands for MATrix Laboratory

Standard Resistor Values: E3, E6, E12, E24, E48, E96

Resistor values are organised into a set of different series of preferred values or standard values.

These standard resistor values have a logarithmically based sequence and this enables the different values to be spaced in such a way that they relate to the component tolerance or accuracy.

Resistor tolerances are generally ±20%, ±10% ±5%, ±2% and ±1%. More accurate tolerances are available for some resistors, but these are not as widely available and costs are higher.

By having these standard resistor values, components from a variety of manufacturers can be chosen, making sourcing much easier and the cost of the components much less.

E-series of preferred numbers

The E-series is a system of preferred numbers (also called preferred values) derived for use in electronic components. It consists of the E3, E6, E12, E24, E48, E96 and E192 series, where the number after the 'E' designates the quantity of value "steps" in each series. Although it is theoretically possible to produce components of any value, in practice the need for inventory simplification has led the industry to settle on the E-series for resistors, capacitors, inductors, and Zener diodes. Other types of electrical components are either specified by the Renard series (for example fuses) or are defined in relevant product standards (for example IEC 60228 for wires).

A decade of the E12 values shown with their electronic color codes on resistors.

Electronic Color Code (R,L,C)

Electronic Color Code  - Resistor, Capacitor and Inductor

An electronic color code is used to indicate the values or ratings of electronic components, usually for resistors, but also for capacitors, inductors, diodes and others. A separate code, the 25-pair color code, is used to identify wires in some telecommunications cables. Different codes are used for wire leads on devices such as transformers or in building wiring.

A useful mnemonic matches the first letter of the color code, in numeric order. Here are two that includes tolerance codes gold, silver, and none:

• Bad beer rots our young guts but vodka goes well – get some now.
• Black Brown ROY of Great Britain had a Very Good Wife who wore Gold and Silver Necklace.

The colors are sorted in the order of the visible light spectrum: red (2), orange (3), yellow (4), green (5), blue (6), violet (7). Black (0) has no energy, brown (1) has a little more, white (9) has everything and grey (8) is like white, but less intense.

Virtual Memory (Computer Operating System)

Virtual Memory

Virtual memory is a memory management capability of an OS that uses hardware and software to allow a computer to compensate for physical memory shortages by temporarily transferring data