[. . . ] First charge: leave the headphones in the charging position all over the night (approximately 15 hours). [. . . ] This headphones transmitter unit has been designed to switch itself off after two minutes if its input level drops below a certain level. This is to comply with the current legislation on reduce the amount of radio emissions in the environment. Therefore, to ensure that this function is not accidentally triggered, we suggest that you set the television, audio amplifier or DVD/CD player headphone volume level at approximately half way (50%). Please consult your equipments user manual for details on how to set the head/earphones volume level. [. . . ] Range (in the open air) : up to 80 m Under no circumstances should this appliance be put to industrial use. [. . . ]