What is a speech generating device?

An electronic device, it is of great use to those with difficulty in speaking. How does it work?

A speech generating device (SGD) is an electronic device that creates speech for those who have difficulty in speaking. Most SGDS are connected to a keyboard, eye sensor or other such keyboard input device that allows the user to select the words to be spoken. The user can enter words or phrases with or use a visual display with images to produce speech.

Digitally recorded human voices speaking actual words are stored in the device and played back upon selection. A variety of voices to match a users gender and age are available. Some SGDS also use computer generated speech similar to the ones used in automated telephone systems.

SGDS have certain advantages over sign boards or other communication methods. It enables a person with speech impairment to communicate through spoken words.

This means the user can easily draw the attention of someone at a distance or sitting in another room or even talk on the phone! SGDS are very effective for autistic children with limited speech ability. World renowned scientist Stephen Hawking used speech generating devices for years. He used to prepare his lectures at the Cambridge University in advance and deliver them using the SGD.

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Are Electricity and Electronics different?

Electricity in a wire creates the pushes and pulls that get work done. It lights lamps and runs machines. But electricity has another important use. It can carry information. Thanks to electricity’s ability to carry information, we have tiny radios, handheld calculators and video games, and personal computers.

The use of electricity to carry electric signals is called electronics. These electric signals may stand for sounds, pictures, numbers, letters, computer instructions, or other sorts of information.

An electronic device has many tiny electrical pathways called circuits. Each circuit has a special job. Some circuits store signals. Others change signals. For example, in an electronic calculator, one circuit might add two numbers together. When the answer is reached, another circuit sends a signal that light up a display screen to show the answer.

The circuits in most of today’s electronic devices are mounted on a chip, a piece of material that is no bigger than a fingernail.

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What is Digital Electronics?


In many electronic circuits, such as those in radios, the current can be of any strength. These circuits are called analogue circuits. In digital circuits, the current can have only two strengths - on and off. Digital circuits are used in devices in which the flow of electricity represents information, such as computers.

Numbers are represented in digital circuits using the binary number system. This uses only the digits 0 and 1 and so can easily be represented in electronic circuits by turning currents on or off. In the decimal system (numbers we use in everyday life: 1, 2, 3, etc.), the digits of a number represent ones, tens, hundreds and so on. In the binary system, the digits represent ones, twos, fours, eights and so on. In digital circuits, each 0 or 1 is called a bit. A four-bit binary “word” can represent decimal numbers up to 15 (one 8, one 4, one 2 and one 1).

Almost any sort of information (from simple letters to complex moving images) can be represented by numbers, which in turn can be represented in binary form. This means that any sort of information can be represented in digital electronic circuits. Computers rely on this fact to store numbers, words, pictures and sounds. They use circuits called logic circuits to process and manipulate the information.

Many types of analogue information must to be turned into digital form before they can be handled by digital circuits. This process is called digitization. For example, in a microphone, a sound, which is created by waves of air pressure, is turned into a changing electric current, called an analogue signal that represents the changes in pressure. This is turned into a digital signal by an electronic circuit called an analogue-to-digital converter. It repeatedly measures the analogue signal, turning it into a continuous stream of binary numbers.

In telephone systems, the sound of your voice is digitized, normally at the telephone exchange, before it travels across the telephone network. Before it arrives at the telephone of the person you are talking to, it is turned back to an analogue signal (which is needed to work the speaker) by a digital-to-analogue converter. The same thing happens in a CD player, because sound is recorded in digital form on a CD.

The pixel code is stored as a binary number, which, inside the computer, exists as electrical signals. 1 means an electrical pulse, 0 means no electrical pulse.


Anything that appears on a computer’s monitor is called computer graphics. These can be as simple as plain white text on a black screen, or as complicated as animated three-dimensional images. Whatever the graphics are, they are made up of small coloured squares called pixels (short for picture elements) in a grid pattern.

The concentration of pixels in a picture is called resolution. High-resolution graphics can be viewed on a large screen without the pixels being visible. Graphics can have a different range of colours, too. In eight-bit graphics, each pixel is represented by eight bits, and so can be any one of 256 colours.

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What are Integrated Circuits?


Single electronic components are normally soldered (connected by metal) on to a circuit board by their legs. Metal tracks on the board connect the components together. Circuits that require hundreds or thousands of components would be enormous. Modern circuits use integrated circuits, or microchips, in which microscopically small components and the connections between them are built into a wafer of semiconductor material, which is normally silicon. This is why integrated circuits are often called silicon chips. There are thousands of different integrated circuits. Some, such as amplifier chips or timing chips, contain a few dozen components. Others, such as computer processors or memory chips, contain hundreds of thousands or even millions.

The first integrated circuit was built in 1959 in the USA by Texas Instruments. Since then the number of components that can be fitted on to a chip has increased rapidly. An integrated circuit starts life as thin wafer of semiconductor material. The components are built into it by adding and removing layers of semiconductor material, conductors and insulators, using complex chemical and photographic processes.

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What do you understand about Electronics?


Electrons are tiny particles that are parts of atoms. An electric current is a flow of electrons. Electronics is the study of how electrons behave and how they can be controlled so that they can do useful jobs. Nearly all the machines we use in our everyday lives - from radios, calculators and television remote controls to telephones, computers and cars - contain electronic circuits that make them work. Electronics are especially important in information technology and communications.

The study of electronics began at the end of the nineteenth century, and had its first practical use in the early 20th century in the development of radio communications. The first electronic devices were called thermionic valves. These included the diode valve, which allowed current to flow through it one way but not the other, and the triode, in which a small current could be used to control a much larger current. The parts of thermionic valves, some of which glowed red hot, had to be enclosed in a glass tube with the air removed to create a vacuum.

In the 1950s valves were quickly replaced by semiconductor devices. A semiconductor is a material that can act as both a good conductor of electricity and an insulator. Semiconductor devices are much simpler, smaller and more reliable than valves.

A thermionic triode valve was designed to amplify (strengthen) electric signals. A central electrode is heated inside a glass tube. Electrons flow from it to another, outer electrode. A small electric signal causes large changes to this electron flow, producing a more powerful electric signal.

There are dozens of different electronic components, but the most common ones are resistors, capacitors, diodes and transistors. A resistor restricts the flow of current in a circuit. Capacitors store electric charge. Current can flow into them until they are full, and out of them until they are empty. A diode allows current to flow one way but not the other. A transistor can act as a switch or an amplifier. It has three connections. The current flowing between two connections is controlled by a tiny current flowing into the third.

An electronic circuit is made up of components linked together by wires around which an electric current flows. By combining different components and connecting them in different ways, it is possible to make electronic circuits which do almost any job. In an electronic circuit, the components of the circuit itself control the current. For example, in a security light, the electric current is turned on or off by an electronic device that detects whether it is dark and whether anybody is moving nearby.

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