AT&T SynJ SB67118 4-Line Extendable Range Corded/Cordless Small Business Phone System Bundle With Expandable Handset Push-to-Talk for instant and easy communication between handsets. DECT 6.0 Zero Blind Slot Digital Technologyup to 10 Accessory handsets active at the same time (number of active outside calls limited by number of outside phone lines) Handset, Speakerphone, Headset and Ringer Volume Control Entry Removal Button. Extendable Rangeup to 980 feet per repeater, up to two repeaters linked for 2940 feet of range.