To make your string telephone all you need is two cups, string, and a pencil to make a hole in the cup.
1st step: Using a pencil make a small hole in the bottom of the cup.
2nd step: Thread the end of the string through the hole and into the cup. Knot the end of the string. I wanted my son to understand how the telephone works. Hence, we used just one cup in our first experience. I tied the free end of the string to a doorknob, and asked my son to walk away from the the door until the string was taut. He held the cup on his ear and I gently strummed and rubbed the string near the doorknob to produce sounds in the cup. The idea was to make him comprehend that telephones have wires, and the sound travels through the wire from one telephone to another.
3rd step: Afterwards we passed the string through the other cup. This time I explained to him that telephones send the sound of voices. We walked away from each other and we started to converse. When I was talking, he was listening and vice-verse.
This is a fun and educational game to play; your children will love it. A great idea for rainny and snowy days :))). Have a great day. Thanks :).