The History of First Mobile Phone (video)

Video courtesy of ColdFusion

The world’s first mobile phone call was made on April 3, 1973, when Martin Cooper, a senior engineer at Motorola, called a rival telecommunications company and informed them he was speaking via a mobile phone. The phone Cooper used, if you could call it that, weighed a staggering 1.1kg and measured in at 228.6x127x44.4mm. With this prototype device, you got 30 minutes of talk-time and it took around 10 hours to charge. 

**This is not paid endorsement**

Read More

Network and Network Criteria

Network

A network is a set of devices (nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending or receiving data generated by other nodes on the network.

Fig: Network

Network criteria

A network must be able to meet a certain number of criteria.

Performance

Performance can be measured in many ways, including transit time and response time. 

• Transit time: The amount of time required for a message to travel from one device to another.
• Response time: The elapsed time between an inquiry and a response.
• Performance factor
1. Number of users
2. Transmission medium
3. Capabilities of connected hardware
4. Efficiency of the software
• Performance evaluated by two networking metrics: throughput and delay. We often need more throughput and less delay.

Reliability 

Reliability measured by

• The frequency of failure
• The time it takes a link to recover from a failure
• The network’s robustness in a catastrophe

Security

Network security issues include protecting data from

• Unauthorized access 
• Damage and development 
• Implementing policies and procedure for recovery from breaches and data losses.

Read More

Data Communication

Data Communication(DC)

Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable, wireless or optical fiber etc. For data communications to occur, the communication devices must be part of a communication system to made up of a combination of hardware (physical equipment) and software (programs).

Characteristics of data communication 

1. Delivery: Must deliver data to the correct destination. 
2. Accuracy: Must deliver the data accurately. 
3. Timeliness: Must deliver data in a timely manner. (For video and audio, timely deliver means delivering data as they are produced, in the same order as they produced and without significant delay. This kind of delivery is called real-time transmission. 
4. Jitter: Jitter refers to the variation in the packet arrival time. (Example: video packets are sent every 30-ms if some of the packets arrive with 30-ms delay and others with 40-ms delay, an uneven quality in the video is the result.) 

Components

There are five components of data communications.

1. Message: text, numbers, pictures, audio, and video. 
2. Sender: person, computer, telephone, video camera etc. 
3. Receiver: same as sender and television. etc. 
4. Transmission medium: cable (twisted-pair, coaxial), radio waves, optical fiber. 
5. Protocol: Protocol is a set of rules that govern the data communications. Actually, it represents an agreement between the communicating devices (sender and receiver).

Fig: 5 components of data communication 

Data Representation

Text 

Texts are represented as a bit pattern, a sequence of bits (0s or 1s). Different sets of bit patterns have been designed to represent text symbols. Each set is called code and the process of representing symbols is called coding. Today, the prevalent coding system is called Unicode, which uses 32-bits to represent a symbol or character used in any language in the world. 

Number

Numbers are also represented by bit patterns. The number directly converted to a binary number to simplify mathematical operations. 

Image 

Images are also represented by bit patterns. First, an image divided into pixels then each pixel is assigned a bit pattern. 

(to know more: http://www.bbc.co.uk/education/guides/zqyrq6f/revision/1)

Audio 

Audio is by nature different from text, numbers, or images. It is continuous, not discrete. 

Video 

Video can either be produced as a continuous entity (TV camera), or it can be a combination of images, each a discrete entity, arranged to convey the idea of motion.

Data Flow 

Communication between two devices can be simplex, half-duplex, or full-duplex. 

Simplex Mode 

In simplex mode, the communication is unidirectional (one-way street). Only one of the two devices on a link can transmit and the other can only receive.

Fig: Simplex

Half-Duplex Mode

In half-duplex mode, each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa.

Fig: Half-duplex

Full-Duplex

In full-duplex mode, both stations can transmit and receive simultaneously.

Fig: Full-duplex

Read More

The Terrifying True Scale of Nuclear Weapons (video)

Nuclear weapons have come a long way and come in all types of different sizes. Some are relatively small while others are enormous, so big they boggle the mind at what they can be capable of. This video analyzes the sizes and impacts of various different nuclear devices, the history of nuclear weapons and what countries in the world are in possession of such devices.

SUBSCRIBE: http://bit.ly/2dB7VTO

**This is not paid endorsement**

Read More

The Biggest Rocket ever Designed (video)

That one rocket, which is still the Tallest, heaviest and most powerful ever built, was the Saturn V, which was designed to take men to the moon and later launched the first American Space station, Skylab. 

But if things had been a little different back in the 60’s we might have had a different rocket to hang on the bedroom walls of the space fans of the 70’s and 80’s.

In the early 1960’s, a rocket was designed which made the Saturn V look small comparison.

This was the Sea Dragon, a super heavy lift rocket that would have been 10 times more powerful with 80 Million lb’s of thrust compared to the Saturn’s 7.8 million and that was from just one massive engine. 

It was designed to lift a payload of 1,100,000 lbs into orbit, compared to the 310,000 lbs of the Saturn V. This meant it could have lifted an entire space station into Low Earth Orbit in one mission.

The rocket bell of this single engine would be so large at 75 feet in diameter, that you could fit the entire first stage of a Saturn V with all 5 of its F1 engines inside with room to spare.

So what happened to the Sea Dragon and why didn’t it get built ?. 

At the time of the design in 1962, it was thought that by the 1970’s, 80’s and beyond, thousands of people would be working in space and on the moon, even on Mars and as such, rockets with huge lifting capabilities would have been in great demand as they would dramatically lower the cost of getting materials into space.

The sea dragon was designed by Robert Truax, a US navy Captain and Rocket engineer. He was one of the pioneers of American rocketry and worked on the Thor and Polaris missiles amongst others. His team debriefed the German Rocket engineers at the end of World War 2 including Werner Von Braun who went on to design the Saturn V.

Traux believed it was complexity that drove up the cost of rockets and not their size. His designs for the Sea Dragon were very simple but very big. The sea dragon would have been 75 ft in diameter and 500ft tall, half the Hight of Chrysler building. 

This type of low-cost super heavy rocket is now known as a “big dumb booster” due to its simplistic design.

Instead of having very complicated turbopump driven engine like the Saturn’s, his were the simplest possible design for a rocket engine. 

In place of having powerful fuel pumps to push the huge amounts of rocket fuel and oxidizer in the engine, he proposed a pressure fed system with a separate liquid nitrogen tank to pressurise the fuel tanks, this would push the fuel into the massive combustion chamber.

His engines were literally not much more than the valves to turn on the fuel and the huge engine bell, this would make them not only much cheaper to manufacture but much easier to refurbish and reuse, unlike the F1 engines of the Saturn which were left crash in the sea and be discarded.

The rocket would be a two-stage design, the first stage would lift it to a height of 130,000 ft before it separated and fell back into the sea, using drag bags to slow it impacts with the water, where it would be recovered for reuse.

Subscribe: https://www.youtube.com/channel/UC726J5A0LLFRxQ0SZqr2mYQ

**This is not paid endorsement**

Read More

What Happened on the Moon Before Apollo? (video)

The Apollo landings from 1969 to 1972 marked a high point in lunar exploration but Apollo didn’t just rock up on to the moon out of the blue, it took many, many missions by probes and landers over the preceding years to establish if we could send men to the moon and get them back

Subscribe: https://www.youtube.com/channel/UC726J5A0LLFRxQ0SZqr2mYQ

**This is not paid endorsement**

Read More