1.  Extension Buttons:  The telephone provides 15 Direct Station Selection/Busy Lamp Field (DSS/BLF) buttons.  Calls can be transferred by pressing a single button.  When the desired extension is busy, the associated LED lights red.

2.  Message:  The MSG (message) button allows this telephone to be used as a message desk.  The secretary/operator can take messages and set message waiting lights on other telephones.  When your message waiting button is lit, you know the operator has a message for you.   (NOTE: With voice mail, message waiting lights are set automatically.) 

3.  Night Answer:  The NA (night answer) button is used to put the system into night mode, automatically rerouting all incoming calls to the designated night answer stations or to the voice mail system.  For example, when the console operator goes home for the evening, pressing the NA button can cause the voice mail system to automatically answer calls.

4.  Call Backup:  The CBU (call back up) button is used to automatically transfer incoming calls to a "backup" answering position.  For example, when the secretary/console operator goes to lunch, calls can be automatically routed to a relief operator.  This means the the relief operator can answer calls from their own desk rather than having to sit at the operator console.

See a description of the other buttons.