A transformer is a device consisting of two or more coils of wire wound on a common core of magnetically permeable material. The number of turns in one coil divided by the number of turns in the other is called the turns ratio. An alternating voltage appearing across one coil will be inducted into the other coil multiplied by the turns ratio. Some transformers are designed to operate at 60 Hz (see WFTD archive “Hertz“) and to handle large amounts of current. They are called power transformers, and are found in almost all electronic equipment to change our 110 volt line voltage to one or more voltages more suitable for operating the device. Audio transformers are designed to operate at audible frequencies, and are used to step audio voltages up or down to send signals between devices such as microphones, tape recorders, mixers, and all types of other electronic equipment. Transformers are also sometimes used in audio to provide isolation between two audio circuits. Because the two coils of wire never electrically touch one another a transformer provides a certain amount of isolation that can help prevent ground loops and other problems that can crop up in complex audio systems.