This is a AM (amplitude modulation) Crystal Radio Kit; but, it uses two transistors to amplify the radio stations. The sound frequencies go through the first transistor (TR1) and increases their strength (amplification); then they go through a 10 MFD capacitor and to another transistor (TR-2), that amplifies them even more. The transistors can be powered by a 9 volt battery; or by a solar cell. The sound amplifies good; and I was able to receive long distance radio reception from Puerto Rico, and Mexico; using a Crystal Radio Long Antenna, and a ground wire.