Factory reset T46s w/o admin password

[DanielP]

For whom it may concern, here the solution which worked for me:
1. Setup a TFTPD Server
2. Put the recovery files into defined tftp folder, T46S.rom, T46S.bin and T46S.rfs
Recovery files can be found here: http://81.88.82.245/firmware/Yealink/recovery/
3. Poweroff and Power-On Phone and keep Speaker button pressed until Display options tftp/usb are shown
4. Select 1- tftp
5. Adjust IP address, netmask and tftpd ip
6. after some few minutes the phone is reset to factory settings