Component of SynJ cordless business phone system, cordless extension deskset supports 4 lines & up to 11 users & is compatible with AT&T SB67118 & SB67138. Built-in DECT 6.0 technology is a frequency band that transmits your voice across multiple channels. This technology provides superior voice & sound quality, high protection against wiretapping & better range than 2.4GHz & 5.8GHz phone systems, while not interfering with wireless routers. Improve customer service with voice mail on every extension. Use the intercom feature for conversations between handsets or between the handset & the telephone base. The Push-to-Talk intercom feature connects you with the other handsets or the base instantly. Cordless phone also features 10 intercom number locations, 10 speed dial numbers, 100-name / number private phonebook directory, digital answering system, hands-free speakerphone, three-party call conferencing, 50-name / number Caller ID / Call Waiting, blue backlit keypad & display.