Section 5 Chapter 29 - Input Output Devices

Question 1

The two versions of barcodes

Answer 1

1D - Linear

2D - QR

Question 2

The four types of barcode readers

Answer 2

• Pen type readers
• Laser scanners
• CCD readers
• Camera based readers

Question 3

How a pen-type barcode scanner works

Answer 3

A light source and photo diode are placed next to each other at the tip of the pen.
The pen is dragged across the barcode at a constant speed.
The photo diode then reads the reflected light and generates a waveform representative of the barcode.
The waveform is then translated to binary and can be used to create and ASCII string

Question 4

Advantage and disadvantge of a pen-type barcode scanner

Answer 4

Durable but limited use as the pen must make contact with the barcode

Question 5

Ideal application of a pen-type scanner

Answer 5

With a laptop computer

Question 6

How a laser scanner works

Answer 6

A laser is shone onto the barcode
The variations in light that is reflected by the black and white stripes are read by a photo diode.
The waveform made by the photo diodes can be translated to binary and then to an ASCII string

Question 7

How a CCD reader works

Answer 7

An array of hundreds of tiny light sensors are lined up in a row at the head of the reader
Each sensor is very small and therefore a voltage pattern identical to the pattern on the barcode is generated in the reader by sequentially reading the voltages across each sensor in the row

Question 8

How a camera based barcode reader works

Answer 8

The camera takes a picture of the barcode which is then interpreted by a piece of image processing software

Question 9

Advantage of a camera based barcode reader

Answer 9

Can read a barcode on any surface, printed or onscreen, badly damaged, poorly printed

Question 10

Common uses of a camera based barcode reader (3)

Answer 10

• Age verification with a driving license
• Couponing
• Event ticketing

Question 11

The two types of digital camera sensors

Answer 11

CCD or CMOS

Question 12

How a digital camera works

Answer 12

A sensor compromising of millions of tiny light sensors arranged in a grid are situated at the back of the lens.
When the shutter opens light enters the camera and projects an image onto the sensors.
Each sensor then measures the colour and brightness of the light it receives.
This is outputted as an electrical signal and is stored as binary data in the camera’s memory card

Question 13

What does RFID stand for

Answer 13

Radio Frequency Identification

Question 14

What is an RFID tag

Answer 14

A tag that is used to identify and track an object

Question 15

Physical difference between active and passive RFID tags

Answer 15

The active tag must have a battery and therefore is much larger

Question 16

Difference in uses of active and passive RFID tags

Answer 16

Active RFID tags are used to track things where the sensor will be much further away.
For instance a car passing through a toll booth

Question 17

How a passive RFID tag works

Answer 17

The radio waves emitted by the reader energise the tag and the transponder in the tag then sends it’s data

Question 18

How a laser printer works

Answer 18

The printer generates a bitmap image and using a laser draws a negative, reversed image onto a negatively charged drum.
The laser causes the parts of the drum that are hit to loser their charge.
The drum then rotates past a toner hopper and toner particles are attracted to the areas which have not been lasered.
The particles are then transferred to the paper and are bound to it with pressure and heat.
If you want colour this process will have to happen 4 times (Cyan, Magenta, Yellow, Black)