Educational Resources
How Phones Work

Vital Stats

Associated Subjects: Science, History, Social Studies
Grade Levels: 4–6
Time Required: One to two class periods
Skills Used: Critical thinking, essay writing, listening, reading, working collaboratively
CO Curriculum Standards Addressed: History 1, 4; Science 1, 2, 5; Reading & Writing 1, 2, 3, 4, 5

Overview

The telephone is a relatively simple device, which accounts in part for its quick spread across the United States and the world after Alexander Graham Bell created the first working set of telephones in 1876. But how does it work? This lesson discusses how our voices are transformed from sound waves into electricity, sent over telephone wires, and then transformed back again almost instantly on the other end.

Resources


Guiding Questions

  • How does a telephone work?

Suggested Activities

You’ve heard of the old tin can and string trick, right? Using two empty tin cans and string, you can make a rudimentary “telephone.” (Click here


Resources
How to Make Tin Cans into Phones

Yes, you really can! Following are directions.


Parts needed:
  • 2 empty and cleaned cans (regular soup size)
  • 2 buttons, no smaller than 1/4 inch in diameter
  • about 20 feet of thin, strong string (6-pound test fishing line works best)
Tools needed:
  • punch (or nail) and hammer, or an electric drill
  • fingers to tie knots in the string
  • file to smooth jagged edge of the hole in the can
How to build the phone:
  • Punch or drill a hole in the center of the bottom of each can. The diameter of the hole should be just big enough for the string to go through. While it's not easy to do, it's best if you can punch/drill from the inside of the can. This allows the button to be as flush to the bottom of the can as possible.
  • Tie the string to one of the buttons.
  • Feed the end of the string with no button through the hole in the bottom of the first can. The button will be on the inside bottom of the can.
  • Now feed the end of the string through the second can, this time from the outside of the can to the inside.
  • Pull the string up from the bottom of the can and tie the second button to it. Pull the button back inside until it rests on the bottom of the can.
How to use your phone:
  • You'll need a partner to talk to on your new phone.
  • Each of you hold one of the cans connected by the string. Get as far from each other as you can without breaking the string. Keeping the string tight between the cans, one of you should hold the can to his/her mouth and talk, while the other person holds the can to his/her ear.
  • The two partners should switch, so that the second speaks into the can and the first listens by placing the can to his/her ear.
Some interesting facts:

String phones were really used, just after the telephone was invented in 1876. Alexander Graham Bell, the inventor of the telephone, had a patent on the regular telephone. There were others who saw how convenient the telephone was, so they manufactured string phones that could transmit a conversation over a distance between two people. The string phones did not infringe on Bell's patent, since they used a different technology. They also didn't work very well and could only be used within 100 feet of each other. The brand name of one of the string phones used in the 1880s was "Thump-a-Phone," since it used a hammer to "thump" on a box (instead of a ringer) to get one's attention.

Several types of string phones were sold in the 1880s, including: Shaver Multiplex Telephone, which came equipped with magneto call bells; Hulls jumbo Telephone; Anti-Bell String phone; Watts String Phone, made from tin and animal skin; the Nile Chair Co. String phone that came with a double funnel to talk into—it seemed to pick up sound waves better; and the Bless Telephone, which came in a box containing two transmitter/receivers and a spool of wire—a portable string phone, just like the one you just made!



for instructions.)

After reading our article about how phones work, have the students describe (in their own words) the way in which Bell’s first telephones worked—which is virtually the same way telephones work today! If your students are particularly hands-on, you can attempt to build your own phone! (Or you can demonstrate it for them.) Contact THG for more information.

Assessment

Have the students write an essay discussing how the phone works, and whether this has changed over time. Alternatively, give them a multiple choice or other exam about the same thing.

Extension

How does a cell phone work? Is it the same principle? How does any wireless phone work?


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Educational Resources
How Phones Work

Vital Stats

Associated Subjects: Science, History, Social Studies
Grade Levels: 4–6
Time Required: One to two class periods
Skills Used: Critical thinking, essay writing, listening, reading, working collaboratively
CO Curriculum Standards Addressed: History 1, 4; Science 1, 2, 5; Reading & Writing 1, 2, 3, 4, 5

Overview

The telephone is a relatively simple device, which accounts in part for its quick spread across the United States and the world after Alexander Graham Bell created the first working set of telephones in 1876. But how does it work? This lesson discusses how our voices are transformed from sound waves into electricity, sent over telephone wires, and then transformed back again almost instantly on the other end.

Resources


Guiding Questions

  • How does a telephone work?

Suggested Activities

You’ve heard of the old tin can and string trick, right? Using two empty tin cans and string, you can make a rudimentary “telephone.” (Click here


Resources
How to Make Tin Cans into Phones

Yes, you really can! Following are directions.


Parts needed:
  • 2 empty and cleaned cans (regular soup size)
  • 2 buttons, no smaller than 1/4 inch in diameter
  • about 20 feet of thin, strong string (6-pound test fishing line works best)
Tools needed:
  • punch (or nail) and hammer, or an electric drill
  • fingers to tie knots in the string
  • file to smooth jagged edge of the hole in the can
How to build the phone:
  • Punch or drill a hole in the center of the bottom of each can. The diameter of the hole should be just big enough for the string to go through. While it's not easy to do, it's best if you can punch/drill from the inside of the can. This allows the button to be as flush to the bottom of the can as possible.
  • Tie the string to one of the buttons.
  • Feed the end of the string with no button through the hole in the bottom of the first can. The button will be on the inside bottom of the can.
  • Now feed the end of the string through the second can, this time from the outside of the can to the inside.
  • Pull the string up from the bottom of the can and tie the second button to it. Pull the button back inside until it rests on the bottom of the can.
How to use your phone:
  • You'll need a partner to talk to on your new phone.
  • Each of you hold one of the cans connected by the string. Get as far from each other as you can without breaking the string. Keeping the string tight between the cans, one of you should hold the can to his/her mouth and talk, while the other person holds the can to his/her ear.
  • The two partners should switch, so that the second speaks into the can and the first listens by placing the can to his/her ear.
Some interesting facts:

String phones were really used, just after the telephone was invented in 1876. Alexander Graham Bell, the inventor of the telephone, had a patent on the regular telephone. There were others who saw how convenient the telephone was, so they manufactured string phones that could transmit a conversation over a distance between two people. The string phones did not infringe on Bell's patent, since they used a different technology. They also didn't work very well and could only be used within 100 feet of each other. The brand name of one of the string phones used in the 1880s was "Thump-a-Phone," since it used a hammer to "thump" on a box (instead of a ringer) to get one's attention.

Several types of string phones were sold in the 1880s, including: Shaver Multiplex Telephone, which came equipped with magneto call bells; Hulls jumbo Telephone; Anti-Bell String phone; Watts String Phone, made from tin and animal skin; the Nile Chair Co. String phone that came with a double funnel to talk into—it seemed to pick up sound waves better; and the Bless Telephone, which came in a box containing two transmitter/receivers and a spool of wire—a portable string phone, just like the one you just made!



for instructions.)

After reading our article about how phones work, have the students describe (in their own words) the way in which Bell’s first telephones worked—which is virtually the same way telephones work today! If your students are particularly hands-on, you can attempt to build your own phone! (Or you can demonstrate it for them.) Contact THG for more information.

Assessment

Have the students write an essay discussing how the phone works, and whether this has changed over time. Alternatively, give them a multiple choice or other exam about the same thing.

Extension

How does a cell phone work? Is it the same principle? How does any wireless phone work?


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