Up to 20 lines and 20 SIP accounts (with DP755), or 10 lines and 10 SIP accounts (with DP752 and DP750) Supports a range of up to 350 meters outdoors and 50 meters indoors with 40 hours of talk time and 500 hours standby time 3-way conferencing Dedicated push-to-talk button, built-in proximity HD audio on the speakerphone, handset, and headset jack Seamless 1-touch door control with Grandstream’s GDS series of Facility Access devices