Component of SynJ cordless business phone system, cordless extension deskset supports 4 lines and up to 11 users and is compatible with AT&T SB67118 and SB67138. Built-in DECT 6.0 technology is a frequency band that transmits your voice across multiple channels. This technology provides superior voice and sound quality, high protection against wiretapping and better range than 2.4GHz and 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 and 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 and display.