Siemens HiPath 4000 Operating Instructions Manual page 50

Telephone settings
Step by Step
SERVICE
-->
PIN / COS?
-->
CHANGE COS
-->
50
Enabling the telephone again:
Press the off-hook key twice.
OK Select and confirm the service menu.
7
Enter the service code.
6
or
Select and confirm.
OK
Select and confirm.
OK
and
p
Enter the PIN (code no.).
OK Press. If the PIN is correct, it will be confirmed with:
"carried out" on the display.