| accessdate=2019-07-25}}</ref> that allows up to six compatible [[Logitech]] human interface devices (such as mice, trackballs, trackpadstouchpads, and keyboards; headphones are not compatible) to be linked to the same computer using [[2.4 GHz]] band radio communication. Receivers that are bundled with a Logitech product are paired with the device at the factory. When purchasing a replacement receiver or connecting multiple devices to one receiver, pairing requires the free-of-charge Logitech Unifying software, available for [[Microsoft Windows]] and [[Mac OS X]]. Although not compatible with [[Bluetooth]], devices pair to Unifying Receivers in a similar way.<ref name=gallegos>{{cite web
