Personal listening systems are portable devices – usually an electronic player attached to headphones or earphones – which are designed for listening to various media, such as music or gaming. The output of such systems varies widely. Maximum output levels vary depending upon the specific devices and regional regulatory requirements.[39] Typically, PLS users can choose to limit the volume between 75 and 105 dB SPL.[2] The ITU and the WHO recommend that PLS be programmed with a monitoring function that sets a weekly sound exposure limit and provides alerts as users reach 100% of his/her weekly sound allowance.