Communication Systems

In this lesson, students model a basic communication system to explore how different components (source, encoder, transmitter, receiver, decoder, and storage) function together to transmit information.

• Both transportation and communication systems are technological systems because they involve interacting parts that work together to solve a specific problem.
• Different parts of a communication system work together to transmit information.
• There are many kinds of communication systems, but they all have similar components.

• How are communication systems similar to transportation systems?
• How do people communicate?
• Why are communication systems necessary for people who want to communicate with others who are far away?
• When have students been the source in a communication system?
• How does encoding change a message from the source?
• Why is encryption sometimes used?
• How do messages move from the source/encoder to the destination?
• Why is decoding important?

Misconception: Radio waves are not related to light at all.

Fact: Radio waves are the longest form of electromagnetic waves, so they are similar to visible light, which is the light we see. The difference is that radio waves carry less energy.

Misconception: Light cannot be used to send information through a communication system.

Fact: Many communication systems use light signals sent through fiber-optic cables. 

Communication system : a group of interacting components that function together to transmit or exchange information between people and/or machines

Decoder : a device that converts a coded communication into a form that can be understood

Encoder : a device that converts information into a format or code so that it can be easily and/or securely transmitted

Receiver : a device that captures incoming signals; often includes a decoder

Source : where information is sent from

Storage : a means of holding information for future use

Transmitter : a device that sends information signals through a channel (air, wires, optical fibers e.g.); often includes an encoder

A 15-Hour Internet Outage

For about 15 hours in February 2015, parts of Arizona experienced an Internet outage. During this time, computers couldn’t get online. Emergency 911 systems were disrupted. This forced emergency responders to use hand-held radios and alternate phone numbers. Businesses couldn’t process credit card transactions. ATMs couldn’t dispense cash.

The problem was first reported around noon on a Wednesday. It wasn’t fully resolved until 3 am the following morning. The Internet service provider for that area said that vandals had sliced through a fiber-optic cable. This cable connects cell phone, TV, and Internet providers with the users of those services.

Internet Communication System

The Internet outage showed how dependent modern society is on the Internet. There are currently more than 1 billion websites. Every day, users send about 269 billion emails and 500 million tweets. They upload 576,000 hours of video to YouTube.

Storage, Transmission, and Receiving

Sometimes information is stored. Storage is a means of holding information for future use. A modern type of data storage is called the “cloud.” The cloud stores information in remote computers connected to the Internet. It can be retrieved anywhere. Retrieval is the accessing of information that is stored. Another form of retrieval occurs when a software application pulls email from an online server or accesses information stored on a hard drive.

Using Internet to Communicate

Communication systems also include a transmitter and a receiver. A transmitter is a device that sends information signals through a channel (air, wires, optical fibers e.g.). Transmitters often have an encoder. A receiver is a device that captures incoming signals. Receivers often have a decoder. Many technologies send and receive information using different frequencies or wavelengths of light.

In Arizona, cell phones, computers, and landlines were knocked out of service because the cable that connected the transmitters and receivers of many communication systems was cut. This cable was a fiber-optic cable. Fiber-optic cables transmit light signals from one place to another.

A cut cable meant that information couldn’t be transmitted from the source to the destination. The destination is the final place where information is sent in a communication system. It is the output of information.

Benefits and Drawbacks of the Internet

The Internet is the ultimate communication technology. It allows people around the world to communicate cheaply and quickly. However, as the cut cable in Arizona showed, there are some drawbacks. Fast and reliable Internet depends on the infrastructure to connect phone and Internet companies with the people who use these services. Many rural areas currently don’t have that infrastructure in place.

Other Forms of Communication

In rural areas, print, audio, and visual technologies are often more reliable. Print includes newspapers and magazines. These printed forms of communication can only be accessed when they are physically in someone’s hands. Today many people can read newspapers and magazines online, but this depends on Internet reliability.

Radios are a reliable source of information in rural areas where the Internet may be spotty. Radios use radio waves to receive information. A radio station uses a radio tower that transmits a certain frequency of radio wave across a wide distance to broadcast music, weather reports, news, and other kinds of information.

The limitation to radio communication is that only those radios within the range of the waves sent by the radio station and tuned to the frequency will receive the sounds that are being broadcast. This form of communication is only one-way. In other words, the radio station can broadcast information, but it doesn’t receive information from radios. In contrast, the Internet has the ability to be two-way communication. People can communicate back and forth with one another very rapidly.

In this lesson, students model a basic communication system to explore phenomena of how different components function together to transmit information.