1. Digital technology
• Contents:
• Base 2 and base 10 number system
• Bits and bytes
• PN diodes
• Boolean logic
• Logic gates
• Digital and analog basics
• Storing devices for digital
• Changing Analog to digital
• How cds store in 1 and 0
• What are CCDs?
• Image capturing
• Sampling for analog to digital conversion
• Work cited pages

2. What are binary digits?
Computers use binary numbers, and
therefore use binary digits in place of
decimal digits. The word bit is a shortening
of the words "Binary digIT." Whereas
decimal digits have 10 possible values
ranging from 0 to 9, bits have only two
possible values: 0 and 1.

3. Decimal and binary numbers.
• You can see that in binary numbers, each bit holds the value of increasing
powers of 2. That makes counting in binary pretty easy
• E.g 1011 means
• 1 * 23) + (0 * 22) + (1 * 21) + (1 * 20) = 8 + 0 + 2 + 1 = 11
• Some more examples
• 10 = 1010
11 = 1011
12 = 1100
13 = 1101
14 = 1110
15 = 1111
16 = 10000

4. Bits and bytes.
• Bits are rarely seen alone in computers. They are
almost always bundled together into 8-bit
collections, and these collections are called bytes.
• With 8 bits in a byte, you can represent 256 values
ranging from 0 to 255, as shown here:
• 0 = 00000000
1 = 00000001
2 = 00000010
...
254 = 11111110
255 = 11111111

5. Bits and bytes continued
• CD uses 2 bytes, or 16 bits, per sample. That gives
each sample a range from 0 to 65,535, like this:
• 0 = 0000000000000000
1 = 0000000000000001
2 = 0000000000000010
...
65534 = 1111111111111110
65535 = 1111111111111111

6. Analog at a glance
As a technology, analog is the process of
taking an audio or video signal (in most cases,
the human voice) and translating it into
electronic pulses. Digital on the other hand is
breaking the signal into a binary format where
the audio or video data is represented by a
series of "1"s and "0"s.

7. A to D
• Digital technology breaks your voice (or
television) signal into binary code—a series of
1s and 0s—transfers it to the other end where
another device (phone, modem or TV) takes
all the numbers and reassembles them into
the original signal. The beauty of digital is that
it knows what it should be when it reaches the
end of the transmission.

8. Is the duplication perfect?
• But like any tansferred technology, digital has
a few shortcomings. Since devices are
constantly translating, coding, and
reassembling your voice, you won't get the
same rich sound quality as you do with
analog.

9. Can we use the digital phone using an
analog line?
• There are digital-to-analog adapters that not only let
you use analog equipment in a digital environment,
but also safeguard against frying the internal circuitry
of your phone, fax, modem, or laptop. Some
adapters manufactured by Konexx come designed to
work with one specific piece of office equipment:
phone, modem, laptop, or teleconferencer. Simply
connect the adapter in between your digital line and
your analog device.

10. Comparing Analog Vs. Digital
• http://telecom.hellodirect.com/docs/Tutorials
/AnalogVsDigital.1.051501.asp
Visit the above site for more details of Analog
Vs. Digital

11. Ancient way of recording the analog way
• In the Beginning: Etching Tin
• Thomas Edison is credited with creating the first
device for recording and playing back sounds in
1877. His approach used a very simple mechanism to
store an analog wave mechanically. In Edison's
original phonograph, a diaphragm directly controlled
a needle, and the needle scratched an analog signal
onto a tinfoil cylinder . (see the clip in the link below)
• http://communication.howstuffworks.com/analog-
digital1.htm

12. An analog wave
Image from
www.howstuffworks.com
Analog Wave
What is it that the needle in Edison's phonograph is
scratching onto the tin cylinder? It is an analog wave
representing the vibrations created by your voice.
For example, here is a graph showing the analog
wave created by saying the word "hello":

13. Analog recording contd….
• The waveform was recorded electronically rather
than on tinfoil, but the principle is the same. What
this graph is showing is, essentially, the position of
the microphone's diaphragm (Y axis) over time (X
axis). The vibrations are very quick -- the diaphragm
is vibrating on the order of 1,000 oscillations per
second. This is the sort of wave scratched onto the
tinfoil in Edison's device. Notice that the waveform
for the word "hello" is fairly complex.

14. Getting in to the digital world
• In a CD (and any other digital recording technology), the goal
is to create a recording with very high fidelity (very high
similarity between the original signal and the reproduced
signal) and perfect reproduction (the recording sounds the
same every single time you play it no matter how many times
you play it). To accomplish these two goals, digital recording
converts the analog wave into a stream of numbers and
records the numbers instead of the wave. The conversion is
done by a device called an analog-to-digital converter (ADC).
To play back the music, the stream of numbers is converted
back to an analog wave by a digital-to-analog converter
(DAC). The analog wave produced by the DAC is amplified
and fed to the speakers to produce the sound.

15. Converting an analog wave to digital wave
• http://communication.howstuffworks.com/an
alog-digital3.htm
Here is a typical wave (assume here
that each tick on the horizontal axis
represents one-thousandth of a
second):

16. ……………..contd…
• When you sample the wave with an
analog-to-digital converter, you have
control over two variables:
• The sampling rate - Controls how many
samples are taken per second
• The sampling precision - Controls how
many different gradations (quantization
levels) are possible when taking the
sample

17. Convert the curve to numbers
• In the following figure, let's assume that the sampling rate is
1,000 per second and the precision is 10:
The green rectangles represent
samples. Every one-thousandth of a
second, the ADC looks at the wave
and picks the closest number
between 0 and 9. The number
chosen is shown along the bottom
of the figure. These numbers are a
digital representation of the original
wave. Want to know the digital form
of this curve? 7 8 9 5 3 4 0 3 7 5
Binary form? For individual digit
7 8 9 and so on
111 1000 1001 …………..

18. • When the DAC recreates the wave from these
numbers, you get the blue line shown in the
following figure:
You can see that the blue line
lost quite a bit of the detail
originally found in the red
line, and that means the
fidelity of the reproduced
wave is not very good. This is
the sampling error. You
reduce sampling error by
increasing both the sampling
rate and the precision

19. In the following figure, both the rate and the precision have
been improved by a factor of 2 (20 gradations at a rate of 2,000
samples per second) and then 4000 samples/sec.:

20. CDs and DVDs.
• http://electronics.howstuffworks.com/cd.htm
• Exploring Sound: Digital Sound
– Laser discs such as CDs and DVDs carry digital
information, which is represented by the binary
code -- combinations of 1s and 0s. Any number
can be represented in binary code. Learn how this
information is encoded in the clip in the above link

21. CD’s and DVD’s
• Data is stored digitally
– A series of ones and zeros read by laser light reflected
from the disk
• Strong reflections correspond to constructive
interference
– These reflections are chosen to represent zeros
• Weak reflections correspond to destructive
interference
– These reflections are chosen to represent ones

22. CD’s and Thin Film Interference
• A CD has multiple tracks
– The tracks consist of a sequence of pits of varying
length formed in a reflecting information layer
• The laser beam shines on a metallic layer
through a clear plastic coating

23. A CD’s pits and bumps
www.physics.byu.edu/faculty/rees/106/PPT/Class26.ppt

24. Reading a CD
• As the disk rotates, the laser
reflects off the sequence of
bumps and lower areas into a
photodector
– The photodector converts the
fluctuating reflected light
intensity into an electrical string
of zeros and ones
• The pit depth is made equal to
one-quarter of the wavelength
of the light
www.physics.byu.edu/faculty/rees/106/PPT/Class26.ppt

25. Reading a CD
• When the laser beam hits a rising or falling bump
edge, part of the beam reflects from the top of the
bump and part from the lower adjacent area
• Light reflecting from the top and bottom of the pit is
a half-wavelength out of phase, so the intensity
drops.
www.physics.byu.edu/faculty/rees/106/PPT/Class26.ppt

26. Reading a CD
• The bump edges are read as ones
• The flat bump tops and intervening flat
plains are read as zeros

27. DVD’s
• DVD’s use shorter wavelength lasers
– The track separation, pit depth and minimum pit
length are all smaller
– Therefore, the DVD can store about 30 times more
information than a CD

28. • In the case of CD sound, fidelity (the similarity
between the original wave and the DAC's
output ) is an important goal, so the sampling
rate is 44,100 samples per second and the
number of gradations is 65,536. At this level,
the output of the DAC so closely matches the
original waveform that the sound is essentially
"perfect" to most human ears .

29. Why is a CD’s capacity approximately
750 mb?
• One thing about the CD's sampling rate and precision is that it
produces a lot of data. On a CD, the digital numbers produced
by the ADC are stored as bytes, and it takes 2 bytes to
represent 65,536 gradations. There are two sound streams
being recorded (one for each of the speakers on a stereo
system). A CD can store up to 74 minutes of music, so the
total amount of digital data that must be stored on a CD is:
44,100 samples/(channel*second) * 2 bytes/sample * 2 channels * 74
minutes * 60 seconds/minute = 783,216,000 bytes (Convert to kbs and
then Mbs.)

30. What is a digital image?
• Essentially, a digital image is just a long string of 1s and 0s that
represent all the tiny colored dots -- or pixels -- that collectively
make up the image. If you want to get a picture into this form,
you have two options:
• You can take a photograph using a conventional film camera,
process the film chemically, print it onto photographic paper and
then use a digital scanner to sample the print (record the pattern
of light as a series of pixel values).
• You can directly sample the original light that bounces off your
subject, immediately breaking that light pattern down into a
series of pixel values -- in other words, you can use a digital
camera
•

31. Capturing image
• The image sensor employed by most
digital cameras is a charge coupled
device (CCD). Some cameras use
complementary metal oxide
semiconductor (CMOS) technology
A CMOS sensor instead. Both CCD and CMOS image
sensors convert light into electrons.
• A simplified way to think about these
sensors is to think of a 2-D array of
thousands or millions of tiny solar
cells.

32. Digitisation of the light
• http://www.olympusmicro.com/primer/digital
imaging/concepts/concepts.html
http://electronics.howstuffworks.com/digital-camera1.htm
The above site has a video clip to explain the digitisation of the light .

33. Digital Camera Resolution
• The amount of detail that
the camera can capture is
called the resolution, and it
is measured in pixels. The
more pixels a camera has,
the more detail it can
capture and the larger
pictures can be without
Photo courtesy Morguefile becoming blurry or "grainy."
The size of an image taken at
different resolutions

34. Capturing Color
• Unfortunately, each photosite is colorblind. It only keeps track
of the total intensity of the light that strikes its surface. In
order to get a full color image, most sensors use filtering to
look at the light in its three primary colors. Once the camera
records all three colors, it combines them to create the full
spectrum
For illustrations and explanations visit:
http://electronics.howstuffworks.com/digital-camera3.htm

35. Work cited pages
• Complete binary mathematics.
• http://www.binarymath.info/
• convert binary numbers to decimals
• http://www.bellaonline.com/articles/art48652.asp
• Basic principles of magnetic recording using digital data in HDD.
• http://www.usbyte.com/common/HDD.htm#top
• storage types
• http://www.jegsworks.com/Lessons/lesson6/lesson6-2.htm
• Details of DVDs.
• http://electronics.howstuffworks.com/dvd3.htm
• Optical recording in a CD.
• http://physicsworld.com/cws/article/print/1383/1/world-11-10-7-2
• Detailed study of dvds and cds comparison. More emphasis on technology of data capture.
• http://www.iti.uni-stuttgart.de/~ghermanv/Lehre/Seminar/material/Presentation4/talk.pdf
• For complete know how on CCDs and image capture in a digital camera
• www.howstuffworks.com