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Flashcards in I/O Devices Deck (18):
1

What is a digital camera?

Device for recording still and moving images in digital form that can then be processed further using specialised software.

2

What are the principles of operation of a digital camera?

• When a photo is taken the shutter opens and lets light in through the lens.
• Light is focused onto a sensor, which is either a charge coupled device ( CCD ) , or a complementary metal oxide semiconductor ( CMOS )
• Sensors are made up of millions of transistors, each of which stores data for one or more pixels.
• As the light hits the sensor, it is converted into electrons and the amount of charge is recorded for each pixel in digital form
• With light, all colours can be created from RGB combinations, a camera will therefore have three different sensors.
• Digital data can be decoded and manipulated using specialist software.

3

Where is data typically stored for a camera?

• Removable storage devices
• Data are usually stored in compressed files.

4

What are RAW files?

Uncompressed files containing all data from the original photograph

5

What are the principles of operation for a camera ( shorthand )?

• Light let in through the shutter
• Focused by the lens
• Directed through RGB filters
• Before being focused onto the CCD or CMOS sensor

6

How is the capability of digital cameras quantified?

How many megapixels it uses to record images.

7

What is the consequence of higher megapixel cameras?

• Higher megapixels mean the sensor is breaking down the image into very small units and taking readings for each unit.
• Image can therefore be recreated very accurately without blurring or pixellation.
• Creating high res images and is useful if the image is going to be printed and enlarged.

8

What are the four types of barcode reader?

• Camera based
• CD
• Laser
• Pen Type

9

What are barcode readers?

Series of input devices that use scanner technology

10

What are the principles of operation of barcode readers?

• A light ( usually LED ) is passed over an image
• Some form of light sensor is used to measure the intensity of light being reflected back, this is converted into a current effectively generating a waveform, this could be achieved using a photo-diode or a CCD sensor in the same way as a digital camera
• White areas reflect most light and black areas the least, making it possible to use the waveform to distinguish patterns of black and white bars
• Waveform is analogue and needs to be converted into digital form using an analogue to digital converter
• Encoding will convert the black and white into binary codes.
• Signal is decoded into a form that can be interpreted by software.

11

Where are barcodes used?

• Primarily for inputting product details at the point of sale.

12

What is RFID?

• Small wireless tracking devices or tags are embedded onto or into other items.
• Tags contain data about the item being tracked.

13

How does RFID work?

• Tag contains a chip which contains the data about the item and a modem to modulate and demodulate the radio signals
• Tag contains an antennae to send and receive signals
• Tags can be active, where they have their own power source, or passive which means they will pick up electromagnetic power when they are in range of an RFID tracker
• Signals and therefore data can be transmitted in both directions using radio frequencies.

14

What are some uses of tags?

• Transmit location
• Transmit data back

15

What are some applications of RFID?

• Tracking individuals
• Use in electronic passports

16

What are the principles of operation of laser printer?

• Rotating drum inside the printer is coated in a chemical which holds an electrical charge
• Laser beam is reflected onto the drum and where the light hits the drum the charge is discharged, effectively creating an image on the drum
• As the drum rotates it picks up toner which is attracted to the charged part of the drum
• Paper is passed over the drum and by charging the paper with the opposite charge to the toner, the toner is attracted to the paper and away from the drum
• Paper is heat treated to fuse the toner onto the paper

17

How is colour printing achieved?

• Four different coloured toners are used, and the process of transferring the toner to the drum is repeated for each colour

18

What is an advantage of using laser printing?

• High speed
• High Quality