Earphones can be used with fixed devices, such as CD or DVD players, home theaters, and personal computers, as well as portable devices, such as digital audio players/MP3 players, mobile phones, etc. Wireless headsets can be connected wirelessly to receive radio or infrared signals, which are encoded by radio or infrared transmission links, such as FM, Bluetooth or Wi-Fi. These are the receiver systems of the power plant, of which the headset is only one component. Wireless headphones are also used in activities such as Silent disco and Silent Gig. Used in audio production environment (2007)
In the field of professional audio, headphones are used in the field, and the signal source is monitored by the disc jockey, DJ mixer and sound engineer. In the broadcasting room, DJs use headphones to speak into the microphone while the speakers are turned off to eliminate acoustic feedback and monitor their own voices. Recording in the studio, musicians and singers use headphones and a backing track to play music. In the military, a variety of audio signals are also monitored through headphones.
Wired headphones are connected to the audio source. The most common connectors are 6.35mm and 3.5mm mobile phone connectors. The largest 6.35mm connector tends to be used in household fixed equipment or professional equipment. Sony introduced a smaller, now widely used, 3.5mm “mini-jack” stereo interface in 1979, adapting the old mono 3.5mm connector to use with Walkman portable stereo tape players. Today 3.5 mm plugs are still a common connector used in portable devices. The adapter can be used to switch between 6.35 mm and 3.5 mm sockets.