You need to start from default configuration / out-of-box status or e.g. recover the phones from password loss? Here is how you can factory reset the devices:

Index:

A) Using the phones web interface

In case you need to reset the H-Series phones to factory default, please try to do this with the help of the web user interface first, - if you can still access it.

1. Inside the web interface select the tab: SERVICING
2. Select the Section: Provisioning
3. Look  for: Reset Configuration and
4. Press the Reset button
5. Following dialog will pop up asking for your confirmation
   
   
   
   
6. When you are sure, press OK

B) Using the buttons on the device

HD100 & HD101 (on the base)

1. longpress ( > 5s) Vol+
2. press Vol-
3. press Vol+
4. press Vol-
5. press Vol+
6. press Vol-
7. press SpeedDial Key 1
8. press SpeedDial Key 2
9. press SpeedDial key 1
10. if completed you will notice a short confirmation sound and the device will reboot, if not managed ( e.g. by provisioning) it will come up on factory default state as desired.
    
    

HD350W & HD351W

1. Dial: * 9 9 0 0 0 0 #
2. if completed you will notice a short confirmation sound and the device will reboot, if not managed ( e.g. by provisioning) it will come up on factory default state as desired.

HM201 (backside of the "hidden" base)

1. Short press for less than 2s to reboot the phone (base)
   or
2. Long press for at least 10s to restore to factory defaults in Static IP mode and then reboot phone (base)