[. . . ] It is technically possible to use an additional number of FM wireless headphones or Philips FM wireless speakers with a single transmitter if they all+: ­ operate in the 864 MHz band ­ work according to the same modulation scheme ­ can detect a 19kHz pilot tone Please consult the appliance's electrical specification sheets for confirmation on compatibility. [. . . ] ~ 15 hours * Specification subject to changes ** Depending on ambient conditions Hereby, Philips Consumer Electronics, B. Peripherals & Accessories, declares that this FM wireless headphone system (SBC HC 8440) is in compliance with the essential requirements and other relevant provisions of Directive 1999/5/EC. This product has been designed, tested and manufactured according the European R&TTE Directive 1999/5/EC. Following this Directive, this product can be brought into service in the following states: This product complies with class 3 requirements as set down in EN301 489-1 and EN301 489-9. If your headphone is experiencing a noticeable degradation in wireless audio quality, first check the possible causes below. If you are unable to remedy the problem by following these hints, check user manual for further details, contact the helpline or consult your dealer. Under no circumstances should you try to repair the set yourself, as this would invalidate the warranty. Adjust the volume level of the headphone, or Adjust the output level of the audio source, which is connected to the transmitter. [. . . ] Com This document is printed on chlorine free produced paper Data subject to change without notice Printed in China [. . . ]