A transistor radio is a portable radio receiver that operates on transistor-based circuitry. Transistor radios were popular electronic communication devices since they were first introduced in 1954. In the 1960s and 1970s, billions of such radios were produced worldwide. Their portability changed the listening habits of people as they could listen to music anywhere on the move. In the 1970s, their popularity declined when other portable media players such as boom boxes and portable cassette players emerged.