Siemens Hicom 150 E optiset E basic Operating Instructions Manual page 16

Requesting work time (wrap-up time)
You have (or had) a UCD connection, before
you replace the handset:
4 0 3
Enter the code
Logging back on after work time
Lift the handset.
4 0 3
Enter the code #403.
Activating UCD night answer
Lift the handset.
4 0 4
Enter the code
Enter the destination number.
Deactivating UCD night answer
Lift the handset.
4 0 4
Enter the code #404.
16
* 403.
* 404.