The concept is fairly simple when it comes to making a microphone out of a speaker element. Once connected to an output jack and hit with audio waves the speaker coil will vibrate  generating AC current. After connecting to an amplifier this current will be transformed back into audio waves. These Telephone Headset Microphones are usually available during our live shows on tour, however now you can get one from the GetLoFi.com/shop. Another example of reusing outdated technology such as a land line telephone receiver in a creative way.