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How to Make a Telephone with Paper and Plastic Cups

With iPhones and Snapchat it’s difficult to imagine kids growing up without the excitement of making telephones out of paper cups and string. It seems like every childhood friendship consisted of wishing you lived close enough to each other to communicate through your bedroom windows with the latest and greatest in “cup and string telephone technology.” It made you feel like you were getting one over on your parents, while it gave you and your friend a sense of adventure and autonomy. Secret late-night chats about hypothetical missions or the latest gossip… those were the days!

Just because we have actual technology, like virtual phone numbers, that lets us do this much easier, does not mean it’s not still fun though, and making telephones is a great ways to teach kids about sound waves and how a traditional telephone works. Let’s take a look at how to make an effective cup and string telephone.

Steps to Make a Telephone out of Paper Cups and String

For materials you’ll need to buy two paper (or plastic) cups and a non-stretchable string, and you’ll need a pair of scissors. Here are the steps to make a paper cup telephone:

  1. Poke a hole in the bottom of each cup with the scissors or another small, sharp object.
    (Optional) Decorate your cups with markers to customize your own personal cup telephone.
  2. Cut the string to your desired length – we recommend you start with anywhere from 60 to 100 feet (we’ll talk about the science behind this later in the post).
  3. Thread each end of the string through the holes in the cups and tie knots in each end to prevent the string from pulling back through the cups. You may also use paper clips to keep the strings attached.
  4. Then, both you and your partner begin walking away from each other until the string is tight. Careful not to rip the string out, but you will need some tension in order for the sound waves to carry.
  5. Finally, as you hold your cup to your ear, your partner can begin sending you secret messages through their cup. Play with the length of the string to see how shorter or longer strings make the message more or less clear. Have fun!

Science Behind the Cup and String Telephone

While this activity is certainly fun and harkens childhood treehouse fantasies, it is also an excellent chance to learn about telephone technology and sound waves. We can communicate with each other because the sound waves our voices make are put out into the air around us. These waves do dissipate if directed into the air, which is why it is easier to hear people that are physically closer to us than farther away – this is why we shout from long distances.

Sounds travel between the two cups through the following process: when the first person speaks into their cup, their voice creates sound waves which then vibrate the bottom of the cup, making it move back and forth about 1000 times per second – or faster! This vibration travels down the string so long as there is tension and it is not a stretchable string (kite string or cotton twine are good ones to use). Once the vibrations reach the other cup, the second person should be able to hear what the first said. You can speak at normal volumes because the sound waves aren’t lost in the air. But, if your string becomes too long, this can also cause the sound waves to weaken and your message won’t be delivered to the other person. This is why it would be fun to experiment with string lengths to see when the message is clearest, and when it starts to fade. You can also experiment with different kinds of cups, whether they are small, big, plastic, paper, or styrofoam. All of these adjustments will affect the clarity and volume of your message.

A traditional telephone operates in much the same way as this rudimentary version. With actual telephones, an electric current replaces the string, and an aspect known as the diaphragm converts your sound waves to electrical energy, and it travels to your friend’s phone via the established telephone network. Transferring the waves to electrical energy allows the waves to travel further. This is a very oversimplified explanation, but for the sake of comparison, it accomplishes the task of comparing the transference of sound waves to a second party.

How Telephones Work Today – Softphones / Virtual Numbers

The technology we use today even with our high tech smartphones is very similar to the technology that has always existed. Instead of converting our sound waves into electrical signals, they are converted to radio signals. Then those signals are picked up by radio towers and sent to our friend’s phone, which then translates those radio signals back to sound waves.

Virtual numbers also work in a similar way. When you buy a virtual number, it is simply a number that is not assigned to a specific telephone line. Instead, these numbers are programmed to be forwarded to another established landline, cell number, or softphone. The rationale behind this is that during the week from 9-5 you can forward the number to your office phone, and on the weekends, you can forward the calls to your cell phone. The reason people find these numbers and this flexibility attractive is that you can give out a local phone number to a local business even though you may be operating your company in an entirely different locale or country. You can even use these phone numbers over the internet on your computer, so if there is no cellular service, but you have wifi, you can still dial and receive calls.

Back to the Basics

No matter how technologically advanced we become as a society, it’s fun to get back to the basics and have some good old fashioned fun with crafts and friends. It’s good to remember the basics behind some of the things we take for granted, especially with the many conveniences of modern technology. Whether you’re in a small midwestern United States town or the bustling city of Toronto, you’ll see folks walking around talking on their cell phones. It’s safe to say that a good portion of these individuals couldn’t tell you how their phones really worked. It might be time for them to sit down and make a cup and string telephone to understand the fundamentals of the amazing technology we have available at our fingertips!

The Invention of the Telephone

Earlier today, Apple unveiled two new iPhones: the iPhone 7 and iPhone 7 plus. The tech giant announced newer models in its immensely popular line of smartphones. Smart phones today come with advanced mobile operating systems, which combine features of a mobile telephone with features of a personal computer.

Mobile telephones like the iPhone are currently some of the most widely used communications devices in the world. In the United States, nearly everyone has a cell phone – including your kids! China has an astronomical 1,100,000,000 cell phones in use.

Although in existence for more than 100 years, telephone usage and demand has been steadily increasing. There is tremendous use for telephones in business communication in addition to the use of personal mobile phones. For such a widely used device, the history of the telephone is rarely discussed.

The History of the Telephone

Alexander Graham Bell’s greatest success was accomplished on March 10, 1876, when he completed a monumentally successful experiment with the telephone. According to his journal entry dated 10 March 1876, Bell spoke these famous words, “Mr. Watson – come here – I want to see you.” This marked the first time he was able to “talk with electricity.”

However, the story behind the invention of the telephone has been surrounded by controversy. Two inventors in the 1870s both independently designed devices that could transmit speech electronically. Within hours of each other, Elisha Grey and Alexander Graham Bell rushed their designs to the patent office.

According to official records, Bell was the first to register his patent by a matter of hours. The two entered a notorious battle over the years regarding the true inventor of the telephone. Alexander Graham Bell emerged as the winner of the legal battle, and thus was declared the official inventor of the telephone.

Telegraphs as a way of communicating

Telegrams were the major form of communication before telephones were invented. For those unfamiliar with telegraphy – a telegram is a message sent by an electrical telegraph operator using Morse code. Users were limited to receiving and sending one message at a time. Telegrams were used to transmit and receive messages over long distances.

Imagine for a second how difficult it was to communicate with somebody using telegraphy. The process required electric telegraph operators, Morse code and wires! Cell phones are so easy to use.

The wire-based telegraph system was highly successful for more than 30 years. The Western Union Telegraph Company bought out smaller companies during the 1800s and rapidly extended its lines to become the dominant player in the early telecommunications industry. In fact, Western Union even built the first transcontinental telegraph line. However, two inventors in the 1870’s would drastically change telecommunications for a long time.

Alexander Graham Bell

Alexander Bell was born on March 3, 1847 in Edinburgh Scotland. Bell’s parents and grandparents were instructors in elocution and the correction of speech. Bell dropped out of high school and university, and his early career involved teaching deaf people. He taught at the Clarke School for the Deaf and at the American School for the Deaf.

While pursuing a teaching career, Bell began researching telecommunications on the side. Bell imagined potential innovations to the telegraph system.

Multiple message telegraphs

Alexander Graham Bell imagined sending multiple messages over the same wire simultaneously. He envisioned a multiple message telegraph that would allow users to send and receive several messages at the same time, rather than a single message.

In 1974, Bell received funding from father-in-law/Boston attorney Gardiner Greene Hubbard to create the “future of telecommunications” – the multiple message telegraph.

Bell worked on the multiple message telegraph and eventually enlisted the services of Thomas Watson, a young electrician. However, the pair began exploring a new idea – developing a device that would transmit speech electronically.

The harmonic telegraph

The two discovered that different tones would vary the strength of an electric current in a wire. Bell and Watson realized they only needed to build two devices for this to work. First, a working transmitter that is able to vary electric currents. Second, a receiver that would reproduce these varied currents.

On June 2, 1875, Alexander Graham Bell was first able to hear sound – a twanging clock spring – over a wire using his “harmonic telegraph” device. Less than one year later, the telephone was born, marking the death of the multiple telegraph idea.

Being able to “talk with electricity” presented vast opportunities to communicate with others.

The future of the telephone

Apple’s announcements today did more than unveil the newest iPhone 7. The announcements showed how far telephones have come. Alexander Graham Bell would probably not recognize his “harmonic telegraphs” today.

Still, the innovations to telephones have been so useful to hundreds of millions of people. Telephones and softphones are still widely used in business today and new features exist that enable landlines to do so much more than transmit voices. In addition, many companies are opting for alternatives to PSTN. Major innovations have altered the field of telecommunications. What’s next?