To begin, know your CO type. Most Northern Telecom DMS ISDN switches follow the ‘Custom’ protocol, sometimes referred to as National ISDN Standard 1 (NI1). However, some DMS ISDN switches are NI2. Most other CO switches follow the NI2 standard…
To change the time on the system from a display phone:
From front desk phone (usually ext. 200)
Press “INT” (do not lift handset)
Press “#” + “652″
Enter the time in Military format
HH:MM:SS (00-23:00-59:00-59)
Press “Redial”
Press “Speaker”