This listening device can pick up distant sounds that are very quiet and clear. It can be used in large meeting rooms, auditoriums, movie theatres, college lecture halls, etc. The circuit can be kept in a shirt pocket in a small plastic box. It's especially good for watching TV at a low volume so as not to wake up other people in the house. A microphone uses electricity to pick up sounds. It's good to use because it has a wide range of frequencies and is sensitive. To make the circuit, you need four transistors and a few resistors and capacitors. Two 1.5V AA-size batteries power the circuit. Transistors T1 and T2 boost the sounds that the microphone picks up. With the 1- mega-ohm resistor R2 in the feedback path, transistor T3 keeps the level steady. This is important because the device needs to make weak sounds louder and weaken loud sounds to a safe level.