KEY FEATURES: Flexible Ringing (on incoming calls on any ext) Call Pickup & Call Waiting Call Transfer - To Extension - To Outside (CO) Line DISA (Direct Inward System Access) with message (3-level, 1ch, 180sec) Music on Hold / Background Music (BGM) Automatic Callback Busy (Camp-on) Limited Call Duration (1~32 minutes) lock target extensions Executive Busy Override (Extension / CO Line Caller ID display on SLT and APT Battery Backup Interface (Built - in) Call Forwarding - All - Busy / No Answer - Follow Me Speed Dialling - System - Personal Door phones, Door Openers, and Doorbells Preferred Line Assignment - Incoming - Outgoing PC programming (USB/RS232C) and easy maintenance Budget management Call charge calculation