Lesson Organizer
Target/Supporting Standards
Understanding analog vs. digital signals: how are they different and why
are digital signals considered more reliable?
07-PS4-3. Integrate qualitative scientific and technical information to
support the claim that digitized signals are a more reliable way to
encode and transmit information than analog signals.
WHST.6-8.9 Draw evidence from informational texts to support
analysis, reflection, and research.
SEP
XCC
Integrate qualitative scientific and technical information in written text
with that contained in media and visual displays to clarify claims and
findings.
Structures can be designed to serve particular functions.
---------------------------------------Technologies extend the measurement, exploration, modeling, and
computational capacity of scientific investigations.
----------------------------------------Advances in technology influence the progress of science and science
has influenced advances in technology.
What students Will Know
Knowledge and Skills
What Students Will be Able to Do
Operational definitions of analog and digital
Understanding of information as intended by the standard
Properties of mechanical waves
Properties of electromagnetic waves
The concept of bandwidth as it relates to information transfer
A variety of ways in which waves can be used to transmit information
Classify signals as analog or digital
Distinguish between mechanical and electromagnetic waves as the
means of transmitting information
Synthesize information from a variety of texts and other resources
Gather data regarding speed and reliability of information transfer for
both digital and analog transmission methods using provided materials
Make a written claim regarding the reliability of digitized signals that is
supported by multiple sources of evidence.
Describe how advances in science and technology have advanced the
ability of people to communicate.
Learning Experience
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Share and discuss organizing question. Focus on meaning of “reliable”—what does it mean for a communication mechanism to be reliable?
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Discuss and reach consensus on the meaning of information, generate class examples of information that can be transmitted through
communication systems of various levels of technological sophistication.
Compare signal quality of the same song stored and transmitted two ways: play same song using an analog record and MP3 player. Discuss
errors in the analog signal (dust, pops, scratches) as compared to the digital version. How is this less ‘reliable’?
Guided reading of resource articles (linked below) comparing analog vs digital signal transmission. Use appropriate differentiated reading
strategies and have students work in pairs to identify main ideas from the texts and journal those ideas.
Have students complete the analog vs digital simulation on individual devices or in groups/whole class depending on access to technology.
Follow with formative question: explain in your own words the difference between an analog and digital signal.
Allow students to interact with mechanical wave communication device (cup and string phones) by having pairs take turns transmitting and
recording a random five digit group of numbers. Increase string length and repeat. Have students document the accuracy of transmission as
string length increases. Ask students to describe through a diagram how the cup phones use mechanical waves to transmit information.
Allow students to interact with light bulb telegraphs made with Christmas tree bulbs and switches. Ask them to brainstorm how such a device
could be used to transmit a signal across a distance, leading into a discussion of how all digital signals require a ‘code’ that is agreed upon by
both the sender and receiver. Provide a copy of the ASCII code and have partners transmit a random five digit number the receiver must record
by observing the light flashes while the transmitting switch is blocked from view. Have them document accuracy of transmission and the
number of individual signals needed to transmit.
Substitute dimmer switches (potentiometers or graphite pencil lead sliders) and have them attempt to transmit another five digit sequence using
an analog code, where each transmission is a varied brightness of the bulb from 0 (off) to 10 (full brightness). Have students document and
compare accuracy of the analog transmission vs the previous digital one while also comparing the number of transmissions needed (40 for
digital compared to 5 for analog) as a way to help them understand the term ‘bandwidth’ as it is used in the texts read earlier. Have students
document how this system uses electromagnetic waves to transmit information and compare to previous diagram of cup phone mechanical
system.
Ask students to work in pairs to devise a way to improve the reliability of the cup phone system by using it to transmit digital vs analog signals,
have them document and share. Examples of solutions might be to devise some sort of code that transmits information by twanging the string or
tapping the cup.
Engage in a discussion of the technological limits of the sample communication systems used in class, brainstorm ways they might be improved
using other knowledge and materials available to them.
Have students work in pairs to engage in research to create a timeline of communication progress. Students choose five technologies that
improved communication (both over distance and asynchronously) and document them on a timeline with notes on which scientific discoveries
or engineering advances made them possible.
Resources and Technology Tools
Interactive comparison of digital vs analog:
http://www.wisc-online.com/Objects/ViewObject.aspx?ID=CIS6108
Comparing analog vs digital chart/article
http://www.diffen.com/difference/Analog_vs_Digital
PowerPoint comparing analog vs digital:
http://www.slideshare.net/ReddyTeja/analog-and-digital-signals-15796948
Simple comparison from How Stuff Works:
http://electronics.howstuffworks.com/question7.htm
Difference between analog and digital signals article:
http://www.differencebetween.net/technology/difference-between-analog-and-digital-signals/
Summative/End of Unit Assessment
Success Criteria
Student is to make a written claim regarding the reliability of digitized
signals as compared to analog signals. This claim is to be based upon and
supported by evidence from text sources as well as data generated from
their classroom experiences using analog and digital transmission
methods to encode and transmit information.
Standard claims/evidence/reasoning rubric.