Unfortunately this is technically not possible.

In order to achieve reliable wireless connection and optimal sound quality, the connection between the base station and the headphone is a unique single digitally controlled link. This link is applicable to the headphone coming with the base station exclusively.

You may be interested in the following analog models if you wish to use more than one headphone with a single base station / transmitter:

• SHC5100 (one headphone in giftbox)
• SHC5102 (two headphones in giftbox)

For the above models, you can use as many headphones on a single base station as you like to.