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Telephone Lines

In this game, the students must pass on the message through a human telephone line.

A telephone is one of the simplest devices you have in your house. In fact, the telephone connection to your house has not changed in nearly a century. If you had an antique phone from the 1920s, you could connect it to the wall jack in your house and it would work fine.

There are two essential parts to a telephone: the microphone (which you talk into) and the speaker (which you put by your ear).

Inside the microphone is a thin piece of metal called a diaphragm. It vibrates when the vibrations from your voice hit it. As the diaphragm vibrates, it wiggles a magnet to make current flow down the wire.

At the other end is a speaker. A speaker has a permanent magnet and an electromagnet inside it. When electric current pulses flow through the electromagnet, it moves back and forth, attracted and repelled by the permanent magnet. This makes a membrane vibrate, which creates sound. Interference is caused by the tiny imperfections in the wires carrying the electrical pulses.

In other words, the telephone system converts acoustic energy (sound) into electric energy. The electric energy travels along the phone wires and is converted back into acoustic energy at the receiving end.

Objectives

  • Describe in simple terms how a wired telephone works.

Materials

  • Per Class or Group:
    something to identify the different teams (coloured shirts, armbands, or flagging tape)
    playing field or gym

Key Questions

  • Did your phone line manage to properly transmit the message?
  • What would have made the message transmitting exercise easier?
  • How does a message transmitted over a long distance compare to one transmitted over a short distance.
  • Could distance affect real telephone conversations as well?
  • What could cause interference along a telephone line?

What To Do

  1. Divide the class into 3 teams (approx. 10 students per team) and label each student with their team’s colour.
  2. One member from each team stands with the teacher at the edge of the field while the rest of their team spreads out on the field (encourage them to cover the whole field—like colours do NOT have to stay together).
  3. Whisper a different message to each team’s leader (they must keep the message safe from the other teams).
  4. The team leader must run to a member of their team and pass on the message. They then take over the second student’s spot as the new runner runs to the next team member.
  5. The students have two objectives: to keep the message safe from the other team and to not let their message get changed as it travels along the “power lines”.
  6. The message must pass through all members of the team.
  7. At the end the last member from each team runs back to the teacher and whispers the message in her ear. The team whose message has changed the least wins!

Teacher Tips:

  • It’s best to explain instructions for the game inside before going outside.
  • As a variation to the game, divide the class into 4 groups, and have each group gather at one corner of the playing area. Show the first group the message. They then run to the second group and find someone to pass the message to. Everyone then runs together to third group and finds someone to whisper the message to. When fourth group is reached, the entire class yells the message out loud.

Extensions

  • Make a telephone out of cans (or plastic containers, or even paper cups) and strings.
  • What could cause interference along a telephone line?
  • Stretch the string taut and speak into one can while your friend listens at the other. How is this similar to how a real telephone works? Hint: Your voice makes the can vibrate and the string carries the vibration to the other can.