The AT&T SB67138 + (3)SB67108 + (1)SB67128 multi-line corded base and cordless system allows expandability up to 10 handsets and features DECT 6.0 Zero Blind Slot Digital technology. This technology increases the radio signal in areas that normally have a weak signal to the base unit. Each extension handset provides individual voicemail, line status, and message waiting indication. It includes 5 extra handsets. Mobile employees have easy access to push to talk, paging, call transfer and 3-way conferencing, you can choose between standard speakerphone and headset operation. The SB67118 speakerphone base supports 4 lines with 100 name and number phonebook directory, power failure protection and automated attendant. The SB67118 can also support up to 6 AT&T booster antennas / repeaters (sold separately). The repeaters extend the range between handset and base by 900 meters. SynJ Extendable Range Phone Systems SMB employees work in a variety of places, from small offices to the largest warehouses. The SynJ extendable range phone system provides cordless handset extensions, Push-to-Talk functionality, up to a half mile of extended range and mobile page and conferencing. SB67138 + (3)SB67108 + (1)SB67128 Features: New DECT 6.0 Technology - Interference Free Communication - Increased Clarity / Enhanced Security - Wider Range / Network Friendly 1.9GHz Corded / Cordless Phone Combo - Dedicated for Cordless Phones by the FCC - 30% Battery Life Increase Over 5.8GHz 4-Line Operation Caller ID / Call Waiting Expandable Up To 10 Handsets 100 Minute Digital Answering System Automated Attendant Time and Day Stamp Call Screening / Intercept Handset Message Access Remote Access Memo Recording Voice Menu Dual Speakerphone (Base & Handset) Large Backlit LCD Display Lighted Keypad 50 Station Name / Number Caller ID Memory 100 Station Phone Directory / Dialer 3-Way Conferencing Music On Hold Compatible New Call Indicator 10 Station Speed Dial Speakerphone Volume Control Selectable Ringtones Handset / Ringer Volume Control Handset to Base / Handset Intercom Call Transfer Page Chain Dial Last 10 Number Redial Hold Mute Line In Use Indicator 2.5mm Headset Jack Bilingual Menu Support (English / Spanish) Voicemail Waiting Indicator