In order to perform a factory reset with your SD series headset, please take the following steps:
1) Ensure that all the power supply are disconnect (both via USB and main supply).
2) Wait a moment to make sure that no residual charge is left in the base station.
3) On the back of the base, press and hold the reset button (the small black button located on the underneath the base station near the white microphone sensitivity dial). You will need to press it with a sharp item, such as a pen.
4) Whilst continuing to press the reset button, reconnect power to the base.
5) Once power has been reconnected, release the reset button.
The base station should now carry out a reset.