Peripheral equipment is often labelled I/O device (Input/Output device). I/O devices are connected to a device controller which is connected to the electronics in the computer system. An example of an output device is a set of computer speakers. Computer speakers are plugged into a device controller called an audio device. The device is connected to the rest of the system inside. An example of an input device is a computer mouse. It is connected in the same way as an output device. Most peripherals connect by cable but some connect by Bluetooth radio.