This chapter begins discussing about an entertainment-type cell phone with a microphone, a receiver, and a “handsfree” loudspeaker followed by the basic design for a cell phone loudspeaker. The electromechanoacoustic circuit for the loudspeaker quantifies this design. A series of design considerations followed by an apparatus for testing the receiver is next. Two types of microphones are discussed: electret and microelectromechanical system. The chapter ends with acoustic measurements for type approval.