Difference Between CDMA and GSM

Parameter	CDMA	GSM
Acronym for	Code Division Multiple Access and also known as IS-95 or CDMAone.	Global System for Mobile Communication.
Technology Used	This Technology is based on spread spectrum technology and does not require dividing the channel by time. It also allows several users to share same frequency in a given band or space. Users are isolated by bipolar sequences and can share same frequency.	In this technology Carrier is divided into number of time slots. These different time slots are assigned to each user and until ongoing call is not finished, no other user can access this assigned slot.
Concurrent User Access	Same frequency is used by several users on the same time and can accommodate more users per MHz of bandwidth than any other technology.	Each user uses separate time slot that can be used by one user at a time.
Network Portability	No such feature is available and hence international roaming is a Problem and very limited support is available.	The availability of Subscriber Identity Modules (SIM) allows users to switch networks.

Difference Between TDMA and FDMA

Parameter	TDMA	FDMA
Acronym for	Time Division Multiple Access	Frequency Division Multiple Access
Technology	In TDMA radio spectrum is divided into time slots and in each slot only one user is allowed to either send or receive.	In FDMA individual channels are assigned to individual users. Each user is allocated a unique frequency or band.
Bandwidth Sharing	In TDMA single frequency is shared by several users.	Frequency sharing is not allowed. If FDMA channel is not in use, it can’t be utilized by other user to increase or share capacity.
Transmission Scheme	Data transmission for users in TDMA is not continuous and uses buffer-and-burst method.	FDMA is a continuous transmission scheme and after the assignment of channel, base station and mobile transmit simultaneously and continuously.

Difference Between 8 bit ISA, 16 bit ISA and EISA

Characteristics	ISA( 8 Bit)	ISA (16 Bit)	EISA
Acronym for	Industry Standard Architecture	Industry Standard Architecture	Enhanced Industry Standard Architecture
Introduced In	1981	1984	1988
Introducer	IBM	IBM	Group of Nine Computer manufacturing Companies Led by Compaq(AST Research, Compaq Computer, Epson, Hewlett-Packard, NEC, Olivetti, Tandy, WYSE, Zenith Data Systems)
Data Bus	8 Bits	16 Bits	32 Bits
Address Bus	De-multiplexed 20 Bit address Bus	24 Bit Address Bus	32 Bit Address Lines
Memory Addressability	1.048576 MB	Up to 16 MB	Up to 4GB

Difference Between Single Mode and Multi Mode Fiber

Parameter	Single Mode Fiber	Multi-Mode Fiber
Core Size	It has very small sized core and allows only one mode of light to propagate.	It has large Sized core and allows multiple mode of light to propagate.
Sources	1310+ nm lasers 1 and 10 Gb/s 1 Gb/s + w/ DWDM High precision packaging	850 nm and 1310 nm LEDs 850 nm lasers at 1 & 10 Gb/s Low precision packaging
Distance Support	This Cable is used to transmit data to long distances. Because as the light passes through the core, the number of light reflections created decreases which decreases attenuation and creates the ability for the signal to travel faster forward. Up to 60 KMs +	This cable is used to transmit data to short distances. Because as the number of lights passes through the core, high dispersion and attenuation reduces the quality of the signal. Up to 2 KMs

SCSI-1,SCSI-2,SCSI-3

SCSI (Pronounced as Skuzzy) is an Acronym for Small Computer System Interface. It is a set of standards for connecting and transferring data between Computer and Peripheral devices. It was developed by Shugart Associates Company in 1981 as a universal and intelligent disk drive interface.

This Interface is generally used for connecting Hard Disk Drives and Tape Drives but can also be used to connect wide range of other devices. This Interface is derived from Shugart Associates System Interface (SASI pronounced as sassy). SASI Controller works as bridge between Disk Drive’s Low level interface and Host Computer. Larry Boucher is considered to be the father of SASI and SCSI. Up to February 1982, ANSI developed this specification as SASI and “Shugart Associates System Interface”. Committee documenting this Standard did not allow it to be named after a company name and after a full day discussion named as SCSI (Small Computer System Interface).

How to Test Power Supply (SMPS)?

Power Supply is the most important part of your computer System because you can not work until your computer is not powering on.  Here I am describing some techniques that you can use to troubleshoot and overcome the SMPS Problems.

Functions Performed

Following Functions are provided by the SMPS (Switch Mode Power Supply):
Its main function is to provide required DC voltage to operate all components in the system.
Different Voltage levels obtained from same power supply.
Output is not affected by the input means if input voltage is between 120V AC to 240V AC the output obtained will be constant. It also provides electrical protection to all components from under voltage or over voltage.
It Provides Necessary Cooling to its components and protects computer from overheating. 

Voltage Levels
If you want to test SMPS than you should know voltage level on every pin of the connector so that testing can be performed:

24 PIN ATX Connector
SIDE A			SIDE B
Pin No.	Color	Voltage Level	Pin No.	Color	Voltage Level
1	Orange	+3.3 Volts	13	Orange	+3.3 Volts
2	Orange	+3.3 Volts	14	Blue	-12 Volts
3	Black	Ground	15	Black	Ground
4	Red	+5 Volts	16	Green	PS_ON
5	Black	Ground	17	Black	Ground
6	Red	+5 Volts	18	Black	Ground
7	Black	Ground	19	Black	Ground
8	Grey	Power good	20	White	NC
9	Purple	VSB  +5V	21	Red	+5 Volts
10	Yellow	+12 Volts	22	Red	+5 Volts
11	Yellow	+12 Volts	23	Red	+5 Volts
12	Orange	+3.3 Volts	24	Black	Ground

 Fig Given Below illustrates these pins on Connector

8 Bit Industry Standard Architecture(ISA) or PC Bus

ISA (Industry Standard Architecture) was first used with the IBM PC in 1981. It was the first open system for PC architecture. No restriction was put on the use of this interconnection method by the IBM. IBM offered free licensing of this PC architecture technique which resulted in more popularity of this. Some main features of 8 bit ISA are:

1) It was introduced by IBM and was the first open system for PC architecture.
2) It provides data transfer rate up to 4.77 Mbps.
3) ISA interface contains 62 pins to interface add on cards. These 62 pins are arranged in two rows, each containing 31 pins.
4) Distance between each pin is 0.1 Inches.
5) 8 Bit ISA make use of Following signals:
    3 Ground Signals
    2 +5V DC Supply
   +12,12,-5V DC supply
    Bidirectional 8 bit data Bus.
   20 Address line, hence memory address space of 1MB (2²⁰=1MB)
   3 DMA request lines
   3 DMA acknowledge lines.
   Six Interrupt Support

Table given below illustrates all signals used by this connector along with their functions:

Functions of North Bridge

After CPU North Bridge is the core chipset on the computer motherboard that controls data communication between CPU and Motherboard. It runs at full processor speed. It mainly works as Memory controller and System Controller. It incorporates interface between Processor and rest of motherboard components.

Chipset is actually numbered according to the number of North Bridge. Nvidia GeForce 320M is a Northbridge /Southbridge fabrication in a single chip. Following are some major functions that are performed by the North Bridge:

Processor Support: Chipset is the major decider on the motherboard that decides which processor is supported, of what speed and how many processors are supported? Following areas are covered by North Bridge under this:

CPU Interface Socket Type: North Bridge is interfaced with the processor through host processor bus and CPU socket. No. of processor sockets are available in the market for this purpose such as Socket 7,Socket -1, Socket A etc. This socket number is decider that which particular Processor class is supported on that motherboard.

Functions of South Bridge

South Bridge is a chipset that is used for controlling I/O Functions such as USB, disk interfaces, PCI Bus, Super I/O Chip support etc. In other words it works as peripheral controller. The main feature of Southbridge is that same South Bridge can be used with different types of North bridges. It is generally located at the lower edge of the motherboard.

Following are some Major Functions Performed by South Bridge:

I/O Control: South Bridge is the key point that decides which kinds of buses, at what speed, and which features will be supported by the system. South bridge controls PCI and ISA buses and transfers information to them or from them.

USB Ports Control: USB Support on the motherboard is provided by the south bridge and which is the main interface for mostly peripheral devices.

Bus Bridge Support: Two main type of buses ISA and PCI are used in most of the modern computers. Since, there is a great speed mismatch between them. South Bridge provides the feature of connecting these two dissimilar buses. This is achieved by PCI-to-ISA bridge chip.

SPX (Sequential Packet Exchange) Protocols

It is the version of Novels’ Sequenced Packet Protocol (SPP). It is a transport layer protocol and is used by client server applications. This protocol provides a packet delivery system for third party applications.

Figure given below illustrate the structure of SPX packet.

Connection Control Flag	DataStream Type
Source Connection ID
Destination Connection ID
Sequence Number
Acknowledge Number
Allocation Number
0-534 bytes of data

Connection Control Flag: Four flags are used to control bidirectional data flow of SPX connection. If its value is 1 flag is said to be set and if its value is 0 it is said to not set. Following are four flags:

How to Download YouTube Videos?

Hello friend today I am going to tell you very special software with the help of which you can download videos from any site like YouTube. Actually this is a plugin that comes with our beloved Mozilla Firefox web browser. So the primary platform to install this plugin is Mozilla Firefox. Here are some important points about this plugin:

Plugin Name is Video Download Helper. It is a tool for web content extraction and can download videos and pictures from other sites.

It’s absolutely free and can be downloaded from official website of Mozilla (Click Here to Download)

No need to install any video downloader.

No Download Limit.

Fast Download Speed.

And one more exciting thing about this plugin is that it can also convert videos into your desired formats during download. Hence we get double benefit Download + Video Conversion.

To perform video conversion another plugin Convert Helper is also installed and can be downloaded from official site at no cost means its also absolutely free. (Click Here to Download)

Another advantage is that you can download videos as per your size means high quality or low quality.

How to Install Download helper?

Here are Some Simple steps that you can use to install and use Video Download Helper.

Intel 8255 (Programmable Peripheral Interface)

Intel 8255 is a PPI (Programmable Peripheral Interface) and is used to interface Peripheral devices to microcomputers. It can be programmed in a variety of ways as per Programmer Requirements. It has two versions 8255A and 8255B. Both of them are similar in general description but are different in their electrical characteristics.

Intel 8255 Consists of Three 8 Bit Ports: Port A, Port B and Port C. The Port C is further divided into two 4 Bit Ports: Port C_UPPER and C_LOWER. These three ports are divided into two groups for the purpose of Programming:

Group A: This Includes Port A (PA₀-PA₇) and 4 MSBs of Port C (PC₄-PC₇).

Group B: This Includes Port B (PB₀-PB₇) and 4 LSBs of Port C (PC₀-PC₃).

Features of 8255A (PPI)

It is a 40 pin IC.
It Operates on single +5V_DCsupply.
Power Dissipation=1 watt.
Ambient Temp. =0- 70 °C
Input Low Voltage (V_IL) = Min. 0.5V, Max. 0.8V.
Input High Voltage (V_IH) =Min. 2V, Max. V_CC.
Output Low Voltage (V_OL) = 0.45V
Output High Voltage (V_OH)= 2.4V
Voltage on any pin 0.5V to 7V.
Darlington Drive Current= Min. 1mA, Max. 4mA.

Pin Description of 8255A

Pin	Description
D0-D7	8 Bit Bidirectional Data Bus and goes to tri state condition if CS is high.
	Chip Select Signal. 8255 is Selected if this pin status is low.
A0-A1	Used to select port from which data is to be transmitted or to which data is to be transmitted.
	Port/Control Word Register	Port/Control Word Register Address
	Port A	00
	Port B	01
	Port C	02
	Control Word Register	03
	To indicate read operation
	To indicate write operation.
PA0-PA7	8 Pins of Port A
PB0-PB7	8 Pins of Port B
PC0-PC3	4 Pins of Port C LOWER
PC4-PC7	4 Pins of Port C UPPER
VCC	+5V DC Supply.
GND	Ground Signal

Operating Modes of 8255A