Siemens HiCom 100 Series

WITH A DISPLAY HANDSET PLUGGED INTO THE FIRST EXTENSION (USUALLY 20 OR 200)
1. Press Service
2. Press Hold
3. Dial 756
4. Press Service
5. Dial 9 * 04 *
6. Dial the hours (00-23) followed by *
7. Dial the minutes (00-59) followed by *
8. Lift and replace the handset