The part of the telephone you put to your ear is called the earpiece or receiver. It's not a capsule, but rather a small speaker that converts electrical signals into sound waves that you can hear.

Here's how it works:

* Incoming sound waves are converted into electrical signals by the microphone in the phone.

* These signals are transmitted to the earpiece.

* The earpiece vibrates in response to the electrical signals, producing sound waves that you hear.

The earpiece is a crucial part of the telephone, allowing you to hear the person on the other end of the line.